Washington — President Trump on Friday told congressional leaders that "hostilities" with Iran have "terminated," addressing a critical 60-day deadline under a law meant to limit the unauthorized use of military force.

"There has been no exchange of fire between the United States Forces and Iran since April 7, 2026," the president wrote in nearly identical letters to House Speaker Mike Johnson and GOP Sen. Chuck Grassley, the president pro tempore of the Senate. "The hostilities that began on February 28, 2026 have terminated."

The framers of the Constitution gave Congress the power to declare war. Nearly two and a half centuries later, that authority is once again at the center of a political and constitutional storm.

At issue is the 1973 War Powers Resolution, a post-Vietnam statute intended to restrain presidential authority and ensure that prolonged military engagements receive congressional approval. But as the war with Iran enters a critical phase, the law's limits — and its ambiguities — are being tested in real time. 

The conflict began on Feb. 28, when U.S. forces, alongside Israel, launched large-scale strikes on Iranian targets, igniting a broader regional confrontation. In the weeks since, Iran has retaliated, global energy markets have been disrupted and the Republican-controlled Congress has been reluctant to assert its constitutional role. 

Under the War Powers Resolution, the president may initiate military action without prior authorization but must notify Congress within 48 hours and terminate hostilities within 60 days unless lawmakers approve an extension. That 60-day clock, triggered by the president's notification to lawmakers on March 2, reached its deadline on Friday — a moment that has sharpened tensions in Washington.

A growing number of Republican lawmakers have said the administration should begin winding down the Iran campaign. Some have said they are working on legislation to authorize the administration to use force against Iran, which would bypass the War Powers Resolution debate altogether.

The Trump administration has argued that the ceasefire brokered in early April effectively terminated active hostilities, and therefore paused the legal countdown. 

Defense Secretary Pete Hegseth on Thursday said that the ceasefire stopped the clock on the 60-day deadline to get congressional authorization.

"We are in a ceasefire right now, which our understanding means the 60-day clock pauses or stops in a ceasefire," Hegseth said during testimony in front of the Senate Armed Services Committee. 

That argument, which the president made explicit in his notification to Congress, did not persuade some lawmakers.

"I do not believe the statute would support that," Democratic Sen. Tim Kaine of Virginia said, adding that the 60-day deadline on Friday would "pose a really important legal question for the administration." 

"We have serious constitutional concerns, and we don't want to layer those with additional statutory concerns," Kaine said. 

Despite the ceasefire, the administration has enforced a naval blockade on Iranian ports, which is considered an act of war, and the U.S. has threatened to imminently restart strikes. Just days after the ceasefire was announced, Hegseth said the military could return to action "at the push of a button."

"We are locked and loaded on your critical dual-use infrastructure, on your remaining power generation and on your energy industry," Hegseth said during a briefing at the Pentagon. "We'd rather not have to do it, but we're ready to go at the command of our president and at the push of a button." 

The U.S. still has more than 50,000 service members in the Middle East. The president said in his letter Friday that those forces are still at risk.

"Despite the success of United States operations against the Iranian regime and continued efforts to secure a lasting peace, the threat posed by Iran to the United States and our Armed Forces remains significant," he said. "Accordingly, the Department of War continues to update its force posture in the [area of operations] in select countries, as necessary and appropriate, to address Iranian and Iranian proxy forces' threats and to protect the United States and its allies and partners."

Congress has never successfully used the War Powers Resolution to end a military campaign, and there are examples of previous administrations interpreting the resolution in such a way that allows military operations to continue. 

"Let me just tell you, on the war powers, so many presidents, as you know, have gone and exceeded it," Mr. Trump told reporters at the White House on Friday. "It's never been used. It's never been adhered to. And every other president considered it totally unconstitutional. And we agree with that." 

In 2011, the Obama administration argued that it did not need congressional approval for air strikes against Libya past the 60-day mark because the operations did not rise to the level of "hostilities." 

During military strikes in Somalia in 1993, President Bill Clinton's administration argued it did not need approval from Congress because the hostilities were not "sustained." During Clinton's second term, the administration continued its bombing campaign in Kosovo past the 60-day deadline, arguing that lawmakers had authorized the operations by approving funding for them.

Mr. Trump vetoed a resolution that sought to end U.S. military involvement in Yemen after it passed both chambers with bipartisan support in 2019. Congress did not have the votes to override the veto.