But in Lebanon, where more than a million people are displaced by the fighting, Israeli forces launched fresh air strikes on Thursday morning, raising doubt about how far Trump will go to force his wartime allies to halt an offensive he has now pledged to end.
Trump put his signature on Wednesday on the "memorandum of understanding" to end the war, as did Iran's President Masoud Pezeshkian, bringing it into effect two days earlier than previously expected.
It calls for the immediate opening of the Strait of Hormuz and lifting of a US blockade of Iran's ports.
Though shippers say it will still take time for transit across the strait to reach pre-war levels, with a need yet to ensure safe access and clear mines, there were immediate signs of an impact.
Ships that once might have concealed their positions by switching off their transponders were now broadcasting their locations, poised to transit the strait.
The US-Iranian memorandum starts the clock on a 60-day negotiation period to reach a final settlement to the war, which Trump launched in February alongside Israeli Prime Minister Benjamin Netanyahu.
But Israel, which launched an invasion in March and has since seized a large swathe of southern Lebanon in its pursuit of Hezbollah militants who opened fire across the border in support of Iran, was excluded from the negotiations.
Iran has always said any peace deal must also cover Lebanon.
In an apparent major concession to Iran, the memorandum signed by Trump explicitly calls for the "permanent termination" of the war in Lebanon and for its "territorial integrity and sovereignty" to be ensured.
With Lebanon among the peace effort's most delicate issues, Trump in recent days has become openly critical of his ally's operations there, accusing Israel of unnecessarily destroying entire buildings to hit Hezbollah fighters.
Two Israeli officials, including a senior official close to Netanyahu, told Reuters on Thursday that Israel was holding negotiations with the US as it seeks to continue its deployment of troops in southern Lebanon.
While fighting in Lebanon tamped down when Trump first announced the deal had been reached, it has ticked up again in the past few days, and continued on Thursday morning after Trump's signature.
Lebanese state media reported air strikes and artillery fire hitting towns in the south, killing at least one person in a car.
The senior Israeli official, who spoke on condition of anonymity to discuss the sensitive talks, told Reuters that Israel was "conducting stubborn negotiations" with Washington over continuing its deployment of troops in southern Lebanon.
Israel would not back down on its position, including that it be permitted to keep troops deployed in what it describes as a buffer zone, south of the Litani River that runs across southern Lebanon.
The second Israeli official told Reuters that the outcome of the talks would ultimately depend on whether Trump "decides to force the issue" by threatening repercussions if Israel does not abide by the interim Iran pact's terms.
The US memorandum of understanding with Iran has largely been lamented in Israel across the political spectrum.
"Soon, Israel may be forced to choose: either keep up the military pressure and lose Trump's diplomatic support, or stay on his good side - but only by ending, or scaling back, the conflict that many see as the country's most urgent fight," the Times of Israel wrote on Thursday.
