Trump says Israel would lead attack on Iran if no deal reached

US President Donald Trump said military action would "absolutely" be the alternative to a nuclear deal and that Israel would lead any attack should talks set to begin on Saturday fail.

"It's a start, we have a little time," he told reporters in the White House on Wednesday, referring to the negotiations in Oman. "But we don't have much time because we're not going to let them have a nuclear weapon."

"(Tehran is) in a rough situation - rough, rough regime - but they understand, and I'm not asking for much. They can't have a nuclear weapon," Trump added.

"With Iran, yeah, if it requires military, we're going to have military. Israel will obviously be very much involved in that. It'll be the leader of that. But nobody leads us. We do what we want to do."