US Defence Secretary Pete Hegseth has argued that the clock has paused on a deadline for the Trump administration to seek approval from Congress for the US-Israeli war with Iran.
Hegseth was responding to questions from members of the Senate, or upper chamber, on Thursday.
Friday is the 60th day since Trump formally notified Congress of the strikes against Iran on 2 March. US law requires a president to "terminate any use of United States Armed Forces" within 60 days of such a notification - unless Congress allows a continuation.
A senior administration official said hostilities with Iran had "terminated", emphasising that a ceasefire had been in effect since early April.
Despite the ceasefire, the two sides have not yet reached a longer-term deal via talks. Meanwhile, the key Strait of Hormuz waterway is still effectively closed - causing economic impacts around the world.
Answering questions from senators on Thursday, Hegseth said: "We are in a ceasefire right now, which our understanding means the 60-day clock pauses or stops in a ceasefire."
The questioner, Democratic Senator Tim Kaine, responded: "I do not believe the statute would support that. I think the 60 days runs maybe tomorrow, and it's going to pose a really important legal question for the administration there."
The relevant piece of US law, the decades-old War Powers Resolution, makes certain requirements of a president "within sixty calendar days" of their use of US armed forces within a combat.
It requires them to end the use of those forces unless Congress makes a formal declaration of war or allows the president an extension, up to 30 days in length, for the "prompt removal" of troops.
The legislation was passed in 1973 to limit the ability of then-President Richard Nixon to continue waging war in Vietnam.
A senior Trump administration official said: "For War Powers Resolution purposes, the hostilities that began on Saturday, February 28 have terminated."
The official highlighted that the initial two-week ceasefire had been extended, and said that there had been no exchange of fire between the US and Iran since 7 April.
The BBC's US partner, CBS News, reported that administration officials were in active conversations with members of Congress about gaining congressional authorisation for the war.
In the case of Iran, Democratic-led attempts in both chambers of Congress to constrain Trump have repeatedly failed. Democrats have vowed to continue their efforts, saying the attempts are an opportunity to get lawmakers' views on the record.
Most Republicans have opposed the Democratic efforts - though some have signalled they could reconsider their positions beyond the 60-day period.
Conflict was sparked across the Middle East after the US and Israel launched wide-ranging strikes on Iran, killing the country's supreme leader. Iran responded by launching attacks on Israel and US-allied states in the Gulf.
The US and Israel have led Western opposition to Iran's nuclear programme, claiming the country is seeking to develop a nuclear bomb - something Tehran has vehemently denied.
US media have given conflicting accounts of the options now being considered by Trump.
Hegseth also sparred with Democratic lawmakers in the House during another hearing on Wednesday.
During that session, one of the defence secretary's top officials revealed that the operations in Iran had cost the US some $25bn (£18.5bn) so far.
Meanwhile, many Republicans on the House committee expressed support for the Pentagon, with congressman Carlos Gimenez of Florida saying he believed Iran was an existential threat to the US.
"When someone tells me for 47 years that they want to kill us, I think I am going to take them at their word," he said. "I support our efforts to make sure that Iran never has a nuclear weapon."
