Washington DC - US forces killed the leader of an Iranian unit that tried to assassinate President Donald Trump, Pentagon chief Pete Hegseth said on Wednesday.

"Iran tried to kill President Trump, and President Trump got the last laugh," Hegseth told a news conference at the Pentagon.

He said the US has known "for a long time that Iran had intentions on trying to kill President Trump and or other US officials."

Targeting those behind that effort was not the main focus of US operations, and Trump never raised the issue, Hegseth said after reports that the assassination risk was one factor in the president's decision to launch the deadly war.

"I ensured, and others ensured, that those who were responsible for that were eventually part of the target list," Hegseth added, without providing further details.

American officials have previously accused Iran of seeking to assassinate Trump to avenge the death of Iranian general Qassem Soleimani, who was killed on the US president's orders in a 2020 drone strike in Iraq.