WASHINGTON — The Senate is expected to vote on legislation as early as Wednesday that would end U.S. involvement in the Saudi Arabia-backed war in Yemen, potentially issuing a major rebuke of President Donald Trump.

The proposal, led by Sens. Mike Lee, R-Utah, and Bernie Sanders, I-Vt., has gained support since the president dismissed the intelligence community’s assessment that Crown Prince Mohammad bin Salman likely ordered the murder of journalist Jamal Khashoggi. The worsening humanitarian crisis in Yemen is also playing a role in senators' frustration with the ongoing war there in which the U.S. is supplying Saudi Arabia with weapons and support to fight the Houthi rebels.

The vote could come after a late morning briefing by Defense Secretary James Mattis and Secretary of State Mike Pompeo for all senators on both issues.

The administration has been putting pressure on the Senate to reject the measure, which would cut off all support for Saudi Arabia's military actions on Yemen.

On the eve of his Senate briefing, Pompeo penned an opinion piece in The Wall Street Journal calling the criticism of Saudi Arabia over Khashoggi's murder a "pile on" and urging senators not to break the Saudi-U.S. alliance.

"Degrading U.S.-Saudi ties would be a grave mistake for the national security of the U.S. and its allies," Pompeo wrote.

But senators on both sides of the aisle were already expressing skepticism about the thoroughness of the briefing, noting that CIA Director Gina Haspel won’t be in attendance. The CIA has concluded that the crown prince was behind the murder, a "high confidence" assessment that Trump has not agreed with.

Sen. Lindsey Graham, R-S.C., and Bob Menendez, D-N.J., wrote a letter Tuesday to Senate leaders, calling it "critical" that Haspel or someone from the CIA conduct the briefing.

"The butchering of a journalist in a consulate on foreign soil, directed by a strategic partner, should be a red line that cannot be crossed without severe consequences for all involved," Graham and Menendez wrote.

In a joint interview with NBC News, Lee and Sanders said there are constitutional issues at stake as well.

"The Constitution is pretty clear that it's the Congress that has the war-making power, not the president,” Sanders said.

Lee added, "The moral issue and the constitutional issue are inextricably intertwined."

The Senate voted on the exact same measure in March but it failed by six votes with most Republicans and a handful of Democrats voting against it.

But on Tuesday, senators who voted against it last time said they are inclined to support it now, including Democratic Senator Chris Coons of Delaware, Republican Jeff Flake of Arizona and the chairman of the Foreign Relations Committee, Bob Corker of Tennessee. But those senators say they want to first hear what administration officials have to say in Wednesday's briefing.

"Frankly it's long past time for us to have a debate on the floor of the Senate about our relationship with Saudi Arabia particularly in the context of the murder of Jamal Khashoggi," Coons said.

And Sen. Jack Reed of Rhode Island, the top Democrat on the Armed Services Committee and a foreign policy hawk, also came out in support of it after opposing it just six months ago. Reed's support was first reported by Rhode Island's WPRI-TV.

But the measure does have detractors who say the Senate should be cautious about interfering. Sen. Roy Blunt, R-Mo., said, "I still think that the Congress isn't the best place to provide for that kind of specific direction right now."