Kaine’s bill would require Trump to cease all hostilities targeting Iran within 30 days unless explicitly approved by Congress. He has modified the original language of the resolution to attract Republican support, including nixing references to Trump. The measure — privileged under the War Powers Act — was on hold during the Senate’s three week impeachment trial, which concluded last week.

Like the Yemen vote, Kaine’s effort will expose long-standing foreign policy divisions within the Republican Party. While the vast majority of Senate Republicans share the party’s historically hawkish positions and supported Trump’s decision to take out Soleimani, several GOP senators have teamed up with Democrats in recent years to force votes to rein in presidential war-making powers.

“I think we’ve abdicated our duty to decide whether we should still be at war or not,” said Paul, who has long opposed U.S. interventions in foreign conflicts and has worked with Democrats over the years on war powers issues. “So the War Powers Act vote for me is just an opportunity to discuss whether or not we should still be at war in Afghanistan or Iraq or any of these places.”

“I’m just ensuring that Congress fulfills our article one responsibilities, that’s all this is about,” added Young.

The views of Paul and Young run counter to those expressed by Senate GOP leaders, who have long supported giving the commander-in-chief wide latitude to order military operations abroad.

“Just as we have successfully sent Iran this strong signal of our strength and resolve, a blunt and clumsy War Powers resolution would tie our own hands,” Senate Majority Leader Mitch McConnell (R-Ky.) said on Tuesday. “With China and Russia watching, is it really a good idea to suggest that we’re willing to let a middling power like Iran push us around?”

While Republicans acknowledge the disagreements within their own party, they have sought to portray the GOP senators supporting Kaine’s bill as outliers.

“I know there are some divisions in our conference, but I think the overwhelming majority [of Republicans] will vote against it for unnecessarily tying the hands of the president,” Sen. John Cornyn (R-Texas). “I mean, we all agree that Congress plays an important role, and we’re not as nimble in actually responding to exigent circumstances.”

Congressional Republicans generally praised Trump for the strike against Soleimani, but Democrats and even some Trump allies questioned the justification for the strike as well as Trump’s authority to carry it out without congressional approval.

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Emerging from an all-senators classified briefing on the Soleimani killing last month, Lee said Trump administration officials advised lawmakers to not debate presidential war powers. Lee called the suggestion “insulting and demeaning.”

“The worst briefing I’ve seen — at least on a military issue — in the nine years I've served” in the Senate, Lee said.

White House and Pentagon officials have repeatedly asserted that Trump had the authority to take out Soleimani, pointing to the 2001 and 2002 authorizations for the use of military force.

Trump himself has expressed disparate views on U.S. involvement in foreign conflicts. While he has campaigned on “ending endless wars,” he has steadfastly resisted congressional efforts to curb U.S. military incursions abroad. Paul, who informally advises Trump on foreign policy and national security matters, has tried to veer the president toward a more non-interventionist posture. But, he added, “We’ve just got to get him some better advisers.”

In the face of a likely veto from the president, Democrats are casting the vote as a symbolic rebuke but also a re-affirmation of Congress’ authority.

“The president will veto it, but it sends a shot across his bow that the majority of the Senate and the majority of the House do not want the president waging war without congressional approval,” Senate Minority Leader Chuck Schumer (D-N.Y.) said. “And once again, the American people are overwhelmingly on our side.”

Kaine said that even if Trump vetoes the resolution, the measure could nevertheless influence his behavior and decision-making when it comes to U.S. policy in the Middle East.

House Majority Leader Steny Hoyer (D-Md.) said on Tuesday that he expects the House to vote on the Senate bill later this month.

Sarah Ferris and James Arkin contributed to this report.

