Congress is set to vote on bipartisan war powers resolutions this week meant to limit President Trump's military operations in Iran.

The dual efforts in the House and Senate face uphill battles to become law, as previous efforts have failed in asserting congressional authority to declare war.

But most Democrats and a handful of Republicans on Capitol Hill still support the effort to curb Trump's use of military power in Iran, after the U.S. and Israel launched attacks against Iran over the weekend that have already claimed the first American casualties.

"The Constitution says we're not supposed to be at war without a vote of Congress," Sen. Tim Kaine, D-Va., a cosponsor of the Senate resolution, told NPR's Weekend Edition. "This is important. The lives of our troops are at risk. We ought to come back to Washington right away and vote on this."

The war powers resolutions had been scheduled for debate and votes before the surprise attack on Iranian military and political leaders. Now that the war is ongoing, it's unclear how or if any successful war powers resolution would immediately change the reality on the ground.

Kaine urged Congress to return earlier than scheduled to vote on the resolutions, but votes on the measures are still expected mid-week.

Congress would likely need to override a Trump veto in order to pass the war power measures. As it stands, it's unclear if there is enough support for initial passage, not to mention the two-thirds majority needed in both chambers to override a veto.

If made law, the measures would block further U.S. military action in Iran without congressional approval under the 1973 War Powers Resolution — which Congress passed during the Vietnam War as a check on executive war authority.

Sen. Mark Kelly, D-Ariz., a Navy pilot and captain, also supports the vote, saying that "Trump has no plan to avoid escalation into a wider conflict that puts more servicemembers in harm's way."

Trump in a video posted online on Sunday said the U.S. would continue its attacks in the Middle East until objectives are met, without specifying what those objectives are.

Administration officials, including the CIA director, defense secretary, and secretary of state, are expected to brief all lawmakers about the Middle East war efforts on Tuesday, the White House said.

'A disastrous vote for any Democrat'

Rep. Ro Khanna, D-Calif., said he gives the House war powers resolution a 40% to 60% chance of advancing out of the House this week.

"It depends if we can keep several Democrats in line," Khanna told NBC News' Meet the Press. "But I believe that this is a disastrous vote for any Democrat — to vote for Donald Trump's war in the Middle East."

He specifically cited Rep. Josh Gottheimer, D-N.J., who has long opposed the Iran war powers resolutions for fear it would "restrict the flexibility needed" in a military operations. Gottheimer didn't immediately respond to a request for comment about his vote.

Most Republicans are expected to stand by Trump's war with Iran and block the resolutions.

"I suspect you'll see overwhelming support from elected Republicans in the Congress," Sen. Tom Cotton, R-Ark., the chairman of the Senate Intelligence Committee, said on CNN Sunday morning.

But Rep. Thomas Massie, R-Ky., one of the sponsors of the resolution in the House, argued that the conflict is not "America First," suggesting some fissures among the GOP; Massie has consistently been one of the few Republicans to vote against some Trump administration priorities.

In the Senate, Sen. John Fetterman, D-Pa., is one of the few Democrats who said he plans to vote against the resolution.

"It's not necessary. Honestly, though, the entire thing, it's really an empty gesture," Fetterman told Fox News Sunday.

These resolution votes comes after the failure of a number of similar attempts to restrict Trump's use of the military without congressional approval.

In June, a Senate vote on Iran war powers failed after the strikes on Tehran's nuclear facilities. And in January, though the Senate narrowly advanced a Venezuela war powers resolution after the capture of former president Nicolas Maduro, the effort ultimately failed to pass.

—NPR's Michele Kelemen contributed to this report.

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