WASHINGTON - The United States' war with Iran has already been "terminated" ahead of a 60-day deadline by law due to the current ceasefire, US media reported on Thursday, citing a senior Trump administration official.

Under the War Powers Resolution, US President Donald Trump had until Friday to seek congressional authorization to continue the conflict or bring it to an end, with the option to extend the deadline by an additional 30 days.

"The hostilities that began on Saturday, Feb 28 have terminated" between the United States and Iran for purposes of that law, the official, who spoke on condition of anonymity, was quoted as saying.

Washington and Tehran have not exchanged fire since a ceasefire began on April 7 and was later extended.

Earlier on Thursday, Defense Secretary Pete Hegseth argued at a congressional hearing that he believes the ceasefire "pauses or stops" the 60-day clock for congressional authorization of war.

"I do not believe the statute would support that," Democratic Senator Tim Kaine responded, "I think the 60 days runs (out) maybe tomorrow, and that's going to pose a really important legal question for the administration there."

"That deadline is not a suggestion; it is a requirement," said Republican Senator Susan Collins, who voted Thursday for a measure to end US military action in Iran without congressional approval.

The White House notified Congress of the military campaign against Iran on March 2, making Friday the 60-day milestone for the president to start winding down the war unless he gets congressional authorization.

On Feb 28, Israel and the United States launched joint attacks on Tehran and other Iranian cities, killing Iran's then Supreme Leader Ali Khamenei, senior commanders and civilians. Iran responded with waves of missile and drone strikes targeting Israel and US assets in the Middle East, and tightened control over the Strait of Hormuz.