Washington DC - President Donald Trump dramatically stepped up his rhetoric against Iran's supreme leader Tuesday, saying on social media that the US knows where Ayatollah Ali Khamenei is located but will not kill him "for now."

In another post, Trump also appeared to demand Iran's "UNCONDITIONAL SURRENDER!" as he fueled questions about whether the United States would join Israel's attacks on Tehran's leadership and nuclear facilities.

"We know exactly where the so-called 'Supreme Leader' is hiding. He is an easy target, but is safe there – We are not going to take him out (kill!), at least not for now," Trump said on his Truth Social platform.

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"But we don't want missiles shot at civilians, or American soldiers. Our patience is wearing thin. Thank you for your attention to this matter!" said Trump.

Minutes later, the US president followed up with another message simply saying: "UNCONDITIONAL SURRENDER!"

Trump flew back early from the G7 summit in Canada late Monday as the conflict between Iran and key US ally Israel escalated, and was set to meet top officials in the White House Situation Room on Tuesday.

The Republican has so far stressed that his country is not getting involved in the conflict, and has said that Iran could still take a deal to end its nuclear program that he had proposed before Israel's attacks.

But Trump has given mounting signals that Washington's intervention in some form may now be imminent.

Trump said Tuesday that "we" have "complete and total control of the skies over Iran," hailing the use of US-made weaponry without explicitly mentioning Israel.

Israel, the closest US ally in the Middle East, had recently made a similar claim.

Earlier, Trump told reporters on Air Force One while returning from Canada that he wanted "a real end, not a ceasefire" to the Iran-Israel conflict, and warning that "I'm not in too much of a mood to negotiate."