Updated at 3:18 p.m. ET

The Senate approved a bipartisan resolution to curb the president's war powers when it comes to Iran — a rare rebuke and effort to reassert Congress' authority,

The vote was 55-45 — with eight Republicans joining all Democrats to pass the measure. The tally fell far short of the two-thirds needed to override a presidential veto.

Virginia Democratic Sen. Tim Kaine led the charge on the resolution, which would ban the president from ordering any new offensive strikes against Iran. It would still allow the president to order strikes in cases of self-defense against an imminent attack.

Early on, the legislation garnered three Republican co-sponsors: Sens. Susan Collins of Maine, Rand Paul of Kentucky and Mike Lee of Utah. And at least one other GOP member, Todd Young of Indiana, said he would support the measure, with other Republicans signaling they would vote yes as well.

"The resolution just says no war with Iran, unless you come and make that case to Congress. And if you make the case to Congress, in front of the American people, and we all have the discussion, ask the tough questions and conclude, sadly, it's in the national interest, that's one thing," Kaine told NPR. "But if we're not even willing to have that discussion, we shouldn't be forcing people to risk their lives."

The move comes more than a week after the Senate acquitted President Trump in a highly partisan impeachment trial. The war powers resolution was filed before the trial began, in the wake of escalating tensions with Iran.

The Democratic-led measure needed at least four Republicans to sign on for the measure to reach the simple majority of the Senate needed for passage — 51 votes.

Lee said the measure focuses on an imbalance of power that has given way to the presidency and it's time for Congress to reclaim its authority.

"We need congressional authorization. We've been lied to by the Pentagon for years regarding a war that has gone on two decades. That's long enough. ... We don't want any more wars without the people's elected representatives being able to debate," Lee said.

Collins said Congress can't be sidelined in these "important decisions."

"It is long overdue," the Maine Republican said. "It reasserts Congress' constitutional role and recognizes that the Framers did not vest in the presidency the authority to declare war unilaterally."

Tensions remain for U.S. and Iran

On Jan. 3, Trump greenlighted a U.S. drone strike that killed a top Iranian general, Qassem Soleimani, which led to increased tensions with Tehran. Iran responded days later by launching more than a dozen ballistic missiles at two military bases in Iraq, which left more than 100 service members with brain injuries.

Soon after, the Democratic-controlled House of Representatives approved a resolution mostly along a party-line vote directing Trump to seek consent from Congress before taking new military action against Iran. However, that resolution was nonbinding.

Supporters say this new Senate version will force the president to make a statement on their concerns. Some maintain that the issue forces debate about what they call "perpetual wars" that need to come to an end.

"I think we've been at war too long in too many places, and it's time to talk about bringing the troops home," said Paul, one of the Republican co-sponsors of the legislation. "It's not so much about rebuking the president — it's rebuking all of us for not giving permission for being at war so long."

The House has signaled that it could pass the Senate version of the war powers resolution. However, Trump has also said he would veto the measure and has lobbied against it.

Still, Kaine holds out some hope for a change of mind in the president since it's an election year, and he says the measure is consistent with Trump's argument that he would end these kinds of foreign entanglements.

"I mean, he might look at it and say, actually, this is kind of what I promised to people," Kaine said. "And he could confound expectations and say the bill gives me the ability to defend us against imminent attack, which I need to have as commander in chief."

Kaine and other supporters have said that even with a veto, the measure sends a strong message to the president to seek lawmakers' approval on such actions and could potentially influence future decisions.

They point to Trump's veto last year of a resolution to end military support of Saudi-led forces in Yemen. However, a few months later, the president ended the refueling of jets aiding the coalition fighting in Yemen.

"So when something like this gets on his desk and represents the majority will of both bodies, he may not care about Congress, but he cares deeply about what the American public thinks about the prospect of another war," Kaine said.

Still, several Senate Republicans spoke against the plan, including Senate Majority Leader Mitch McConnell, R-Ky., who voted against it. He suggested supporters should wait until they garner a two-thirds majority of the Senate, or the 67 votes needed to override a veto.

"This war powers resolution cuts short that interplay between the branches. It short-circuits the thoughtful deliberation and debate," he said. "It's a dangerously overbroad resolution that should not pass Congress and is certain to be vetoed if it does."

Gaining bipartisan support for the measure

Kaine introduced the first version of his war powers resolution within hours of the Soleimani attack on Jan. 3. He revised it with help from a group of Republicans to gain their support and filed an updated resolution days later. The new version, for example, removed direct references to Trump

Young, who is a Marine Corps veteran, says his military background played a role in his decision to support the measure. "It's really important that Congress fulfill our constitutional responsibilities, which is to declare war, to authorize the use of military force and to engage in these debates on a consistent basis as long as we have men and women overseas ready to put their life on the line for all of us."

The war powers concern is tied to a long-running debate on whether the president should be relying on authorizations issued in the wake of the Sept. 11 attacks.

Congress approved the wide-ranging Authorization for Use of Military Force efforts in 2001 and 2002. And Trump administration officials have maintained that the president already has the authority to take action against Iran under the 2002 authorization.

Kaine said that at minimum, service members deserve a debate on whether the U.S. should enter into new wars. And this isn't the first time GOP lawmakers have split from the White House to pass a war powers resolution.

Last June, Collins, Lee, Paul and Sen. Jerry Moran of Kansas backed an amendment to the National Defense Authorization Act to require congressional approval for action against Iran. However, the effort ultimately failed at that time by a 50-40 vote.

This time Kaine strove to increase support for the plan by working one-on-one with Republicans to tweak the legislation in their favor.

Lee publicly signed on to the measure after a contentious closed-door January briefing on Iran with Trump administration officials. Lee said he found the briefing, which included Secretary of State Mike Pompeo, "insulting and demeaning" and an attempt to quash any dissent on the Iran attack that killed Soleimani.

It reaffirmed for him that he should support the war powers measure, he said.

"This is one that is neither liberal nor conservative. It's neither Democratic nor Republican. ... This is neither hawkish nor dovish," Lee argued this week. "This is something that simply focuses not on whether war is ever appropriate, not on whether some action against or involving Iran might at some point become necessary or warranted. It focuses instead on the fact that moving forward, any action that we take involving Iran ... needs to be authorized by Congress."

But Sen. Marco Rubio, R-Fla., agreed with other detractors that the measure sends a problematic message that Congress and the administration aren't on the same page.

"It sends a message to adversaries that the president somehow doesn't have support or the power to act defensively if we come under attack," Rubio told NPR. "They are not going to read the language. They are just going to view it as a rejection of the president acting forcefully to either prevent an attack against Americans or respond to one."

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