"The deal's all signed," Trump told reporters after arriving in France for a summit of the Group of Seven major economies.
Trump said US Vice President JD Vance would attend a formal signing ceremony in Geneva on Friday.
The agreement would reopen the strategic Strait of Hormuz, a key shipping route for global oil and gas supplies, and extend a ceasefire for 60 days to allow negotiators to address unresolved issues, including the future of Iran's nuclear programme.
Many details of the agreement have yet to be disclosed, but it appears to be the most significant step so far toward ending a conflict that has killed at least 7,000 people and rattled global energy markets, the Reuters news agency reported.
Further details are expected later this week.
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Source: Reuters, PAP, IAR