Washington • President Donald Trump personally ordered his staff to freeze more than $391 million in aid to Ukraine in the days before he pressed the new Ukrainian president to investigate the Democrats’ leading presidential candidate, two senior administration officials said Monday.

Trump issued his directive to Mick Mulvaney, the acting White House chief of staff, who conveyed it through the budget office to the Pentagon and the State Department, which were told only that the administration was looking at whether the spending was necessary, the officials said.

The timing of the decision to block the aid and Trump’s personal involvement, which were first reported by The Washington Post, add vital new elements to the raging debate over the president’s effort to persuade Ukraine to examine unsubstantiated corruption allegations involving former Vice President Joe. Biden and his son Hunter Biden.

The revelation came as leading congressional Democrats demanded that the administration turn over documentation about the matter, as a flood of their colleagues said, before news of Trump’s involvement in freezing the aid, that the president’s actions could warrant impeachment.

Several House Democrats from more moderate districts who had long resisted such a move added their voices Monday to calls for an inquiry that could lead to charges of high crimes and misdemeanors against the president.

Trump, buffeted by questions earlier in the day at the United Nations about his conduct, denied that he withheld the aid from Ukraine in an attempt to press President Volodymyr Zelenskiy of Ukraine to dig up dirt on the former vice president.

“No, I didn’t — I didn’t do it,” Trump told reporters. But just moments before, he suggested that there would be nothing wrong with linking American funding for Ukraine, a former Soviet republic that is fighting Russian-backed separatists, to a corruption inquiry about Biden and his family.

“Why would you give money to a country that you think is corrupt?” Trump said.

It was one of a series of whipsawing declarations Trump made throughout the day Monday as he defended himself, vilified the Bidens and appeared by turns eager and reluctant to reveal the facts at the root of the allegations. Trump first said he hoped that the transcript of a July 25 phone call he had with Zelenskiy would be released, claiming that it would exonerate him, only to angrily deny moments later that he had committed to doing so.

“I hope you get to see it soon,” Trump said, before arguing that making the transcript public would set a bad precedent — a position that one person familiar with White House deliberations said was being advanced by Secretary of State Mike Pompeo.

Biden chimed in via the president’s favorite platform, Twitter, responding to Trump’s dismissal of charges of misconduct by writing, “So release the transcript of the call then.”

Trump has acknowledged raising Biden and the corruption questions with Zelenskiy in the July 25 telephone call. People familiar with the conversation said Trump repeatedly urged his counterpart to speak with Rudy Giuliani, the president’s personal lawyer, who has been pushing Ukraine aggressively to look into the Bidens and any contacts that the previous government in Kiev had with Democrats during the 2016 campaign.

Trump did not discuss the delay in the military assistance on the July 25 call with Zelenskiy, according to people familiar with the conversation. A Ukrainian official said Zelenskiy’s government did not learn of the delay until about one month after the call.

Congressional Democrats have said that if the president really pressured Ukraine for dirt on a domestic political rival, it could be an impeachable offense whether or not he tied the demand to American aid. But if evidence emerges that the president linked the two, it would likely bolster the case of critics who call that an abuse of power.

The decision to hold back the aid, which had been approved by Congress, came at a time when the president was looking for ways to curb a variety of foreign assistance programs and some aides at least initially saw it in that broader context. But Trump singled out Ukraine as a place he considered corrupt and railed about wasting money there, according to people who heard him discuss the matter, and he questioned the aid package for weeks.

The president asked advisers how to think about Zelenskiy, a former comedian outside the Ukrainian establishment who was largely unknown to American policymakers and had shown little interest in Giuliani’s calls for investigations related to U.S. politics.

It soon became clear that the Ukraine aid freeze was different from the hold placed on other programs. Even after other foreign aid was restored, the money for Ukraine remained blocked.

The suspension of the aid caused confusion and frustration in both Washington and Kiev for months. Zelenskiy and other Ukrainian officials were mystified and complained to visiting U.S. lawmakers. For five years, Russia has sponsored separatists in eastern Ukraine and the government in Kiev had relied on American and European security aid.

American government officials were left in the dark as well. When staff members at the State Department and Defense Department who work on issues related to Ukraine learned of the holds in July, they were puzzled and alarmed, according to current and former government officials familiar with the situation.

Pentagon officials tried to make a case to the White House that the Ukraine aid was effective and should not be looked at in the same manner as other aid. But when those arguments fell on deaf ears, and when the other aid was allowed to move forward, the Pentagon officials began to wonder what the real reason for the White House skepticism was, the former official said. State Department officials began to contact the offices of members of Congress considered sympathetic to the cause.

The assistance came in two pots overseen by different agencies — $250 million from the Defense Department’s Ukraine Security Assistance Initiative and $141 from the State Department’s foreign military financing program. The funds were intended to help train and equip Ukrainian forces in their fight to stave off Russian incursion.

Congressional committees had approved the defense assistance to the Ukrainian military in two separate tranches — the first in early April and the second in early June, shortly after the Pentagon submitted the spending for approval, according to the officials.

That cleared the way for the administration to finalize the release of the assistance. The Defense Department had already begun processing some of those funds and officials worried that if the White House did not release the funding before the end of the fiscal year on Sept. 30, it would be lost.

Defense and State Department staff were frustrated when they sought explanations or resolution from the White House Office of Management and Budget and contacted the offices of members of Congress considered sympathetic to the cause.

Lawmakers pressed the administration on why the Ukraine aid was being held, but were first told the assistance was being reviewed to determine whether it was in the best interest of foreign policy. Other administration officials said, without detail, there was a review on corruption in Ukraine, according to current and former officials. Then as August drew to a close, other officials told lawmakers they were trying to gauge the effectiveness of the aid, a claim that struck Congressional aides as odd, the officials said.

But Vice President Mike Pence later said that the review was based on concerns from the White House about “issues of corruption.” Without detailing those concerns, Pence, after a meeting with Zelenskiy in Warsaw on the sidelines of a commemoration of the outbreak of World War II, told reporters that “to invest additional taxpayer in Ukraine, the president wants to be assured that those resources are truly making their way to the kind of investments that will contribute to security and stability in Ukraine.”

A handful of Republican and Democratic senators who belong to a bipartisan Ukraine caucus wrote a letter to Mulvaney this month expressing “deep concerns” over the delay in releasing the funding. The funding is “vital to the long term viability of the Ukrainian military,” helping it “fend off the Kremlin’s continued onslaughts within its territory,” the senators wrote.

Pressure on the White House from Republican senators intensified. Sen. Rob Portman of Ohio spoke to Trump about the funds, and Sen. Lindsey Graham of South Carolina informed the White House that he planned to support an amendment by Sen. Dick Durbin, D-Ill., that would block Pentagon spending to ensure that the Ukraine funds were released. On Sept 11, the administration told lawmakers it would release the funds.

Two days before, Rep. Adam B. Schiff, the California Democrat who leads the House Intelligence Committee had released a letter he had sent to the acting director of national intelligence revealing the existence of a whistleblower case that might involve the president — touching off a series of disclosures in the press that brought the controversy over the Ukraine aid to a full crisis.

House Democrats on Monday moved to try to force Trump’s hand, even as they weighed voting on a resolution this week condemning his actions. At the same time, the chorus of lawmakers demanding impeachment grew louder, underscoring how the latest revelations about the president have touched off a seismic shift under Democrats’ feet.

Seven freshman House Democrats with military and national security experience — most of whom have been reluctant to call for impeachment — spoke out Monday night in a strongly worded opinion article in The Washington Post.

“If these allegations are true, we believe these actions represent an impeachable offense,” the lawmakers wrote.

The authors were Reps. Gil Cisneros of California, Jason Crow of Colorado, Chrissy Houlahan of Pennsylvania, Elaine Luria of Virginia, Mikie Sherrill of New Jersey, Elissa Slotkin of Michigan and Abigail Spanberger of Virginia.

The chairmen of three House committees investigating the matter threatened to issue subpoenas in the coming days if the administration did not hand over a transcript of the call and documents related to the decision to withhold the aid money. A failure to do so — or to disclose to Congress a secretive whistle-blower complaint said to be related to the Ukraine matter — would be considered obstruction, they said, an indication that they could consider it grounds for impeachment.

“If press reports are accurate, such corrupt use of presidential power for the president’s personal political interest — and not for the national interest — is a betrayal of the president’s oath of office and cannot go unchecked,” the chairmen of the House Intelligence, Foreign Affairs, and Oversight and Reform Committees wrote Monday in a letter to Pompeo.

They added, “By withholding these documents and refusing to engage with the committees, the Trump administration is obstructing Congress’s oversight duty under the Constitution to protect our nation’s democratic process.”

It appeared increasingly likely that the brewing conflict would come to a head Thursday, when the House Intelligence Committee was already scheduled to question Joseph Maguire, the acting director of national intelligence, who has withheld the whistleblower complaint under advisement from the Justice Department and the White House. The panel has demanded that Maguire bring with him a copy of it.

Now, lawmakers also want a decision by Pompeo — and by extension, Trump — by that day on whether he will furnish a transcript of the presidential conversation, as well as other materials they have requested.

Mindful that Democrats may have only a brief window to decide their course, Speaker Nancy Pelosi summoned the leaders of six House committees involved in investigations of the president to meet Tuesday, telling the lawmakers to come without aides. Afterward, she planned to convene a special meeting of the Democratic caucus to discuss impeachment.

Their decisions could have grave implications for Trump’s presidency.

A growing number of House Democrats said Monday that the new revelations all but demanded the move. They warned that a decision by the Trump administration not to hand over documents about a matter of urgent national security would leave the House with no choice but to initiate full-bore impeachment proceedings. At the same time, they said, any material that corroborated news reports about Trump’s actions could lead to the same outcome.

“It is clear that the sitting president of the United States placed his own personal interests above the national security interests of the United States,” said Rep. Angie Craig of Minnesota, who flipped a Republican seat last fall. She called for impeachment proceedings to begin “immediately, fairly and impartially.”

Craig’s announcement came alongside that of another Minnesota freshman, Dean Phillips, who warned, “If the reports are corroborated, we must pursue articles of impeachment and report them to the full House of Representatives for immediate consideration.”

Slotkin, a former CIA officer who participated in briefings with Presidents George W. Bush and Barack Obama, and who advocated whistleblower protections while working for Bush’s director of national intelligence, said the issue was “personal” for her.

“As national security professionals, this was too much,” she said. “While we had always been judicious in thinking about impeachment before, this just crossed a line.”

Other, more veteran lawmakers, issued similar statements.

Veteran Democrats close to Pelosi, who has stubbornly resisted impeachment, joined the chorus as well. “An impeachment inquiry may be the only recourse Congress has if the president is enlisting foreign assistance in the 2020 election,” said Rep. Rosa DeLauro of Connecticut. “Congress must meet this pivotal moment in our nation’s history with decisive action.”

There were also indications of more movement to come. Other moderate freshmen who have shied away from impeachment spent the day furiously calling one another in efforts to calibrate their responses. Several said privately that they were on the brink of supporting an impeachment process, but that they wanted to first see what transpired Thursday.

Privately, some Democrats and their aides were more cautious, fretting that the transcript of the July call would not be as damning as billed. They worried that the anticipation of its disclosure was replicating the dynamic that surrounded the release of the report by Robert Mueller, the former special counsel who investigated Russia’s interference in the 2016 elections, in which Democrats had expected a set of clear-cut revelations that would all but demand Trump’s impeachment, but ended up instead with a document that did not move public opinion against the president.

Democrats got some backup in the Senate from Republicans, who have generally split over whether Trump is obliged to share either the transcript or the whistleblower complaint with Congress.

“I believe the most helpful report would be a transcript of the president’s conversation with President Zelenskiy,” Sen. Mitt Romney of Utah, the 2012 Republican nominee for president, told reporters. “That, I think, would be the most instructive. But I certainly believe that the whistle-blower report should also be available to Congress.”

Speaking on the Senate floor Monday afternoon, Sen. Mitch McConnell, R-Ky., and the majority leader, accused Democrats of trying to exploit a serious issue for political gain. He said he had confidence that the Senate’s intelligence panel, working quietly on a bipartisan basis, would handle it appropriately.