Iran's supreme leader threw his support behind the elite Revolutionary Guard in a rare sermon on Friday after their belated admission that they had accidentally downed an airliner triggered days of street protests.

In his first Friday sermon in eight years, Ayatollah Ali Khamenei also told worshippers chanting "Death to America" that the elite Guard could take their fight beyond Iran's borders after the U.S. killing of a top Iranian commander.

U.S. President Donald Trump hit back later on Twitter, writing that Khamenei should be careful what he says.