Speaking on the sidelines of the G7 summit, Trump defended the 14-point memorandum of understanding with Iran that has yet to be made public.
"The only thing that really matters to me is Iran will never have a nuclear weapon, and it says it loud and clear," he told reporters, warning "all hell will rain down" on Iran if it sought to acquire one.
In 2015, former US President Barack Obama secured a nuclear deal with Iran in exchange for sanctions relief, a process that took two years to finalise. Trump withdrew the United States from that accord during his first term.
"This deal is a wall to a nuclear weapon. His (Obama) deal was a road to a nuclear weapon. My deal, they can't have a nuclear, they get blown up," Trump said.
Diplomats and analysts note Iranian negotiators are highly skilled in nuclear diplomacy, often exploiting weaknesses in their counterparts and buying time to advance their agenda, making the prospect of a comprehensive agreement within 60 days challenging.
One key factor in whether the interim accord holds will be the situation in Lebanon, where Israeli Prime Minister Benjamin Netanyahu has said his troops would remain in the south as long as needed to tackle Hezbollah. Tehran has demanded an Israeli withdrawal.
Trump appeared critical of Israel's strategy in Lebanon and also suggested that neighbouring Syria - which under President Ahmed al-Sharaa is struggling to stabilise the country after years of civil war - could be best placed to intervene.
"I suggested to Israel to let Syria take care of Hezbollah because to be honest, I think they do a better job of doing it," he said.
The agreement on Monday would extend a tenuous ceasefire announced in April by another 60 days and reopen the Strait of Hormuz.
Negotiators would address difficult issues like the future of Iran's nuclear program during the next phase.
"The deal's all signed," Trump said after he arrived in France for a summit of the G7 group of big economies.
He said Vice President JD Vance would attend a formal signing ceremony in Geneva on Friday.
The deal is the most significant step yet to resolve the conflict, which has killed at least 7000 people, mostly in Iran and Lebanon, and upended global energy markets. But much about the agreement remains unknown, and whether its provisions differ from the April ceasefire was unclear.
Iranian President Masoud Pezeshkian wrote on social media the US-Iran memorandum of understanding was an "important step" toward stopping the fighting but noted a final agreement for a lasting truce "has yet to take shape".
Trump appears to have achieved little of what he said he intended when he launched strikes on Iran with Israel on February 28. Iran's theocratic government remains in place, while his demands that Iran dismantle its ballistic missile program and end support for regional militias like Hezbollah remain unmet.
The new agreement also does not resolve the fate of Iran's stockpile of enriched uranium, which Trump says he wants destroyed or removed.
Iranian officials, who have always denied intending to build a nuclear weapon, say they have given up little by agreeing to resume the diplomatic discussions with Trump officials over the nuclear program that were interrupted in February by Trump's decision to launch the war.
While the latest agreement lifts Iran's chokehold on the Strait of Hormuz, that only restores the prewar status quo, and shippers say traffic will only restart once safety is assured.
Iran has suggested it will retain control with Oman over the strait. The US said the strait will be open toll-free for 60 days and it would expect that provision to be part of a final agreement as well.
with PA
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