Negotiations between Iran and the United States over Tehran’s rapidly advancing nuclear program will return Saturday to the secluded sultanate of Oman.

Donald Trump has threatened air strikes if no deal is reached, while Iran hints it may pursue nuclear weapons with its growing uranium stockpile.

The Trump administration is prepared to allow Iran to have a civil nuclear program that relies exclusively on imported nuclear fuel, Secretary of State Marco Rubio said, outlining a possible compromise with Tehran aimed at preventing it from building a nuclear weapon.