US President Donald Trump said the United States could restart the war or become the "guardian of the Middle East" and receive 20% of the region's revenues if Iran fails to reach an acceptable agreement on its nuclear programme.

Speaking after announcing an agreement with Iran that is expected to reopen the Strait of Hormuz and end months of conflict, Trump said future negotiations would focus on Tehran's nuclear programme and warned of consequences if talks break down.

Trump pointed to the reopening of the vital shipping lane as a key achievement of the agreement in a phone interview with The New York Times. Iran, however, had not imposed tolls before the conflict, meaning the arrangement would largely restore conditions that existed before the war.

The president said if Iran failed to come to an adequate agreement about the future of its nuclear program in the coming weeks, he would either restart military attacks or make the US “the guardian of the Middle East” in return for 20% of the region’s revenues.

Trump's remarks underscored the high stakes surrounding the next phase of negotiations, with the future of Iran's nuclear activities expected to become the central focus of talks following the signing of the agreement.