President Donald Trump has claimed he had secured assurances from Iran that it would not develop nuclear weapons, amid reports that Washington had sent a revised peace proposal with tougher terms back to Tehran.

Any tweaks to the proposal could further delay an agreement to formally end the Middle East war and open the Strait of Hormuz maritime route, after weeks of efforts to secure a deal despite fractious rhetoric and the occasional flare-up of armed conflict.

The New York Times and Axios reported Saturday that Trump had sent back a new framework for Iran to consider with "tougher" terms, though it was not immediately clear what that entailed.

Trump has said his priorities for any deal include stopping Iran from any nuclear weapon development and reopening the blockaded Strait of Hormuz.

"The one guarantee that I have to have is that there will be no nuclear weapons. They've agreed to that, and it was very interesting," he told his daughter-in-law, Lara Trump, in an interview broadcast on her Fox News program on Saturday night.