US President Donald Trump rejected a plan by Israel to kill Iran's Supreme Leader Ayatollah Ali Khamenei, three US officials have told BBC's US partner CBS News.

Trump reportedly told Israeli Prime Minister Benjamin Netanyahu that assassinating Khamenei was "not a good idea", according to one official. The president has not commented publicly on the report.

The conversation is said to have happened since Israel launched its attack on Iran on Friday.

During an interview with Fox News, Netanyahu did not directly confirm or deny a report from Reuters that Trump had vetoed a plan to kill the ayatollah.

"There's so many false reports of conversations that never happened and I'm not going to get into that," the Israeli prime minister said.

"But I can tell you I think we do what we need to do. We will do what we need to do and I think the United States knows what is good for the United States and I'm just not going to get into it."

An Israeli official told CBS News that "in principle" Israel does not "kill political leaders, we are focused on nuclear and military. I don't think anyone making decisions about those programs should be living free and easy".

Israel first launched an attack on Iranian nuclear infrastructure and other targets on Friday. The two countries have continued to launch massive strikes at each other since, with attacks entering a third day on Sunday.

In his latest post on Truth Social about the escalating situation in the Middle East, Trump said "Iran and Israel should make a deal", adding that he would get the two to cease hostilities "just like I got India and Pakistan" - referring to the recent confrontation between the countries.

Speaking to reporters before leaving for the G7 summit in Canada, Trump said the US would continue to support Israel and declined to say if he had asked the country to stop its strikes on Iran.

The next round of US-Iran nuclear talks were initially scheduled to take place on Sunday, but mediator, Oman's foreign minister Badr Albusaidi, announced a day earlier that they had been cancelled.

Iran told Qatar and Oman that it was not open to negotiating a ceasefire while it was still under Israeli attack, an official briefed on the communications told the Reuters news agency on Sunday.

Trump said on Saturday that the US "had nothing to do with the attack on Iran".

"If we are attacked in any way, shape or form by Iran, the full strength and might of the U.S. Armed Forces will come down on you at levels never seen before," he warned.