Rome • Secretary of State Mike Pompeo confirmed on Wednesday that he had listened in on President Donald Trump’s telephone conversation with the president of Ukraine — a call that has become the subject of a whistleblower’s complaint and is at the heart of an impeachment inquiry by House Democrats.

“I was on the phone call,” Pompeo said at a news conference in Rome — the first time he has addressed the topic publicly since reports surfaced that he had heard the exchange.

He did not elaborate on the conversation and did not answer a question about whether anything in it had raised a red flag for him.

In the July 25 call, Trump pressed President Volodymyr Zelenskiy of Ukraine to investigate the activities in Ukraine of former Vice President Joe Biden and his son Hunter.

Zelenskiy thanked Trump for U.S. assistance in defending Ukraine against Russia, and said his country wanted to buy more American weapons. Trump, who days earlier had frozen an aid package for Ukraine, replied, “I would like you to do us a favor though,” and asked for help in investigating the 2016 election.

An anonymous whistleblower within the government filed a complaint in August, citing the call and other factors as information that “the President of the United States is using the power of his office to solicit interference from a foreign country in the 2020 U.S. election.”

The complaint, made public last week, says that White House officials, rather than storing a record of the conversation with Zelenskiy in the usual computer system, attempted to “lock down” information on it, placing it in a more secure system, accessible to fewer people, because they “understood the gravity of what had transpired in the call.”

Pompeo’s confirmation that he was on the call came as he engages in a fight with Democrats in the House of Representatives who have demanded swift access to State Department officials for interviews as part of the impeachment inquiry.

And it came on a day when Congress may receive new information about the Trump administration’s interactions with Ukraine, from the State Department inspector general, Steve A. Linick, who requested to meet committee staff members on Wednesday.

Pompeo on Wednesday described U.S. policy toward Ukraine as “remarkably consistent,” being focused on addressing “the threat that Russia poses” and attempts at “helping the Ukrainians to get graft out, and corruption outside of their government.”

“Even,” he added, “while all this noise is going on.”

Current and former State Department officials have said it is unusual for a secretary of state to listen in on presidential calls with other world leaders. That is normally a role filled by the White House national security adviser and the National Security Council staff.

Pompeo supports a get-tough policy on Russia and may have been included on the call to ensure that message was reflected in Trump’s comments to the Ukrainian president.

John Bolton, another Russia hawk who then was serving as national security adviser, often disagreed with Pompeo, and they competed for Trump’s ear. Since Bolton was ousted last month, Pompeo’s influence has grown.

In his request to Zelenskiy, Trump pushed a conspiracy theory that his own staff had repeatedly told him was false — that Ukraine, not Russia, had intervened in the 2016 election and that it had done so on behalf of the Democrats.

In another call, to Prime Minister Scott Morrison of Australia, Trump asked for help discrediting the Mueller investigation into Russia’s election interference.

Trump has repeatedly vented his anger at the impeachment inquiry on Twitter, asking why he was not “entitled to interview” and know the identity of the whistleblower, whose anonymity is protected by law to prevent retaliation. He has also tweeted that he is the target of an attempted coup and that Rep. Adam B. Schiff, D-Calif., the chairman of the Intelligence Committee, should be arrested.

On Tuesday, Pompeo released a letter that excoriated House Democrats for demanding quick depositions of State Department officials involved in policy toward Ukraine, calling it an “act of intimidation” that did not allow his officials sufficient time to respond.

“What we objected to was the demands that were put that deeply violate fundamental principles of separation of powers,” Pompeo said on Wednesday. “They contacted State Department employees directly, told them not to contact legal counsel at the State Department — at least that’s been reported to us — told them State Department wouldn’t be allowed to be present.”

He said that the department would cooperate with Congress, but that, “we won’t tolerate folks on Capitol Hill bullying and intimidating State Department employees — that’s unacceptable.”

The House postponed the first of the depositions, which it had scheduled for Wednesday.

Rep. Elijah E. Cummings, the chairman of the House Oversight and Reform Committee, accused Pompeo of obstruction.

“In response, Congress may infer from this obstruction that any withheld documents and testimony would reveal information that corroborates the whistle-blower complaint,” Cummings said in a statement.

In response to Pompeo’s letter, he wrote that House Democrats believed Pompeo had an “obvious conflict of interest” because of his presence on Trump’s call with Zelenskiy and that they would not inform Pompeo about other witnesses.

“The committee may infer that he is trying to cover up illicit activity and misconduct, including by the president,” the statement read.