At 6 pm local time in Sweden, confirmation of a settlement came - which will also include resumed oil transport through the Strait of Hormuz.
When Wall Street closed just under four hours later, the Dow Jones industrial average had risen 0.9 percent, the broad S&P 500 index 1.7 percent and the technology-heavy Nasdaq composite index 3.1 percent.
This is about the same level they were at before Trump's statement, which he and Vice President J.D. Vance had signed digitally, as had Iranian Parliament Speaker Mohammad Bagher Ghalibaf.
The Dow closed at a new record high.
The futures price for North Sea oil also did not move significantly, remaining at $83.7 per barrel.
SpaceX rose 19.6 percent, after rising 19 percent at Friday's IPO.
