Washington • House Democrats on Wednesday will launch their bid to block the Trump administration from completing 22 arms deals largely benefiting Saudi Arabia, but hurdles in the Senate — and expected veto threats — could undermine a bipartisan effort to prevent the president from completing the deal in defiance of Congress.

Members of the House Foreign Affairs Committee are expected to unveil four resolutions of disapproval Wednesday, each designed to push back on elements of President Donald Trump's plan to conclude the arms deals via an emergency executive order. One resolution aims to block all 22 deals, while the other three specifically address the sale and production of precision-guided munitions to and within Saudi Arabia and the United Arab Emirates.

Many lawmakers oppose the proposed sales, particularly those that benefit Saudi Arabia, a country to which bipartisan majorities in Congress have sought to restrict arms transfers and military aid over the kingdom's intervention in Yemen's civil war and its leaders' suspected role in the killing of Saudi journalist Jamal Khashoggi. But still more lawmakers have bristled at the administration's tactic of claiming a blanket, nonspecific emergency to justify the move, objecting to it as an executive power grab of Congress's traditional right to raise objections to such transactions.

The House proposal is a twist on the strategy that Sens. Robert Menendez, D-N.J., one of President Trump’s most vocal critics, and Lindsey Graham, R-S.C., one of his closest allies, spearheaded last week to block the deals using 22 unique resolutions that, under normal circumstances, would be guaranteed floor votes. But while such votes are all but guaranteed in the Democrat-controlled House, in the GOP-led Senate, critics of Trump’s arms deals are bracing for a struggle — and preparing alternate options in case their first attempt fails.

Menendez is expected to request a vote on the Senate’s 22 disapproval measures early next week. But Republicans may challenge him — leaving it to the Senate parliamentarian to act as referee. The parliamentarian determines how the Senate’s rules should be applied, and is often called upon to settle procedural disputes between lawmakers.

"We'll see how the parliamentarian rules," said Senate Foreign Relations Committee Chairman James Risch, R-Idaho, noting that "I suspect someone will ask" the parliamentarian to determine whether the measures should get a vote.

Senate Majority Leader Mitch McConnell, R-Ky., on Tuesday surmised there “would still be a vote triggered,” and “presumably it’ll be very similar to the resolution of disapproval under a more traditional approach — at least that’s what we think the parliamentarian believes.”

But McConnell pledged to oppose efforts to block Trump's move, "voting against the resolution of disapproval and for sustaining the veto when it comes to that."

At present, more than 50 senators are expected to vote for the 22 resolutions to block the president, including four Republicans: Sens. Graham, Todd Young, R-Ind., Rand Paul, R-Ky., and Mike Lee, R-Utah. While that is enough to pass the resolutions, it is not clear that enough Republicans will join the effort to secure the two-thirds majority it takes to overcome a presidential veto.

Should efforts fail to build a veto-proof coalition around that approach, Young and Sen. Chris Murphy, D-Conn., have proposed another, which would give lawmakers the chance to block the arms sales after requesting information on the human rights record of the recipient countries.

But that would take several weeks, due to the time allotted for the administration to respond to the human rights query — making it an unlikely option before lawmakers depart Washington for an August recess, according to congressional aides, and subject to the same potential veto as the 22 resolutions.

Opponents of the sales also are plotting ways to amend a prohibition on the arms sales into must-pass measures, such as the annual defense authorization bill, or appropriations measures currently working their way through Congress. But Republican leaders are firmly opposed to such an approach, favoring independent legislation.

"I'm doing my best to negotiate a bill that can pass both the House and Senate and be signed by the president," Risch said Tuesday. "There are ongoing negotiations among all parties, State Department and all others to try to reach an agreement on this."

But thus far, senior State Department officials have been unrepentant about circumventing Congress to complete the sales.

"These sales and the associated emergency certification are intended to address the military need of our partners in the face of an urgent regional threat posed by Iran," R. Clarke Cooper, assistant secretary of state for political-military affairs, is expected to tell the House Foreign Affairs Committee on Wednesday, according to prepared remarks. "Remaining a reliable security partner to our allies and friends around the world is also in the interest and furtherance of our values."

When asked Tuesday whether the administration was wise to force the arms deals through by emergency declaration, acting defense secretary Patrick Shanahan was more tight-lipped.

"It's always best to follow the process," he said.

The Washington Post’s Emily Davies, Hailey Fuchs and Missy Ryan contributed to this report.