Trump said in a post on Truth Social that a ceasefire between Israel and Iran was now in place.
His announcement came only hours after Iran launched waves of missiles, which Israel's ambulance service said killed four people.
Trump says a ceasefire is now in effect
When Trump announced on Monday what he called a complete ceasefire to end a 12-day war, he appeared to suggest that Israel and Iran would have time to complete missions that were underway, at which point the ceasefire would begin in a staged process.
Witnesses said they heard explosions near Tel Aviv and Beersheba in southern Israel before Trump's statement.
Israel's military said six waves of missiles were launched by Iran and Israel's national ambulance service said four people were killed in Beersheba, the first reported deaths in Israel since Trump announced the ceasefire.
Iran's semi-official SNN news agency reported on Tuesday that Tehran fired its last round of missiles before the ceasefire came into effect.
A senior White House official said Trump had brokered a ceasefire deal in a call with Israeli Prime Minister Benjamin Netanyahu and Israel had agreed so long as Iran did not launch further attacks.
An Iranian official earlier confirmed that Tehran had agreed to a ceasefire, but the country's foreign minister said there would be no cessation of hostilities unless Israel stopped its attacks.
Abbas Araqchi said early on Tuesday that if Israel stopped its "illegal aggression" against the Iranian people no later than 4 a.m. Tehran time (0030 GMT) on Tuesday, Iran had no intention of continuing its response afterwards.
