The Senate approved a rare bipartisan measure on Thursday limiting President Donald Trump's authority to launch military operations against Iran.
The measure, authored by Sen. Tim Kaine, D-Va., says Trump must win approval from Congress before engaging in further military action against Iran. Eight Republicans joined with Democrats to pass the resolution by a 55-45 vote.
Kaine and other supporters said the resolution was not about Trump or even the presidency but instead was an important reassertion of congressional power to declare war.
While Trump and other presidents must always have the ability to defend the United States from imminent attack, the executive power to initiate war stops there," Kaine said. An offensive war requires a congressional debate and vote."
The Democratic-controlled House passed a separate, nonbinding war powers resolution last month. The House could take up the Senate resolution later this month, said House Majority Leader Steny Hoyer, D-Md.
Two-thirds votes in the House and GOP-run Senate would be needed to override an expected Trump veto.
Answering a claim by some of Trump's supporters and Trump himself that the measure would send a signal of weakness to Iran and other potential adversaries, Kaine said the opposite was true.
"When we stand up for the rule of law - in a world that hungers for more rule of law - and say 'this decision is fundamental, and we have rules that we are going to follow so we can make a good decision,' that's a message of strength," Kaine said.
Sen. Mike Lee, R-Utah, agreed. Lee supports Trump's foreign policy, including toward Iran, but said Congress cannot escape its constitutional responsibility to act on matters of war and peace.
Trump disputed that, arguing in two tweets Wednesday that a vote against Kaine's proposal was important to national security and pointed to the Jan. 3 drone strike that killed Iran's top general, Qassem Soleimani.
"We are doing very well with Iran and this is not the time to show weakness. Americans overwhelmingly support our attack on terrorist Soleimani," Trump said. "If my hands were tied, Iran would have a field day. Sends a very bad signal. The Democrats are only doing this as an attempt to embarrass the Republican Party. Don't let it happen!"
Tehran responded to the U.S. attack on Soleimani by launching missiles at two military bases in Iraq that house American troops. The attack caused traumatic brain injuries in at least 64 U.S. soldiers, the Pentagon said.