Trump says US will 'completely decimate' Iran if assassinated

President Donald Trump said Friday the United States would "completely decimate" Iran if it attempted or succeeded in assassinating the sitting president.

"1000 Missiles are Locked and Loaded and aimed at the Islamic Republic of Iran, with thousands of more to immediately follow, should the Iranian Government act on its threat, pronounced in many corners of the Globe, to assassinate, or attempt to assassinate, the sitting President of the United States of America, in this case, ME!," Trump wrote on his social media platform Truth Social.

"Orders have already been given, and the U.S. Military is ready, willing, and able, for a one year period of time, subject to extension, to completely decimate and destroy all areas of Iran," he said.

Meanwhiule, Iran's supreme leader on Saturday vowed revenge for the US-Israeli killing of his father and predecessor, hours after President Donald Trump warned against any attempt to assassinate him.

Both sides dialled up the rhetoric after exchanges of fire this week rocked an interim agreement aimed at ending their war, which broke out in late February with massive US-Israeli strikes.

Trump has declared their ceasefire over, while mediators have been trying to salvage diplomacy, with Iranian media reporting that a delegation from Qatar travelled to Iran on Friday.

"Vengeance is the will of our nation and must inevitably be carried out," Mojtaba Khamenei said in a written message.

He became Iran's supreme leader after his father Ali Khamenei's killing in late February by US-Israeli strikes, but has not been in public since before the war.

"This matter depends neither on my personal existence nor on that of other officials. Whether we are present or not, it will come to pass," he wrote in his first message since his father's funeral this week.

He said Iran had compiled a list of individuals to be targeted.