For President Trump, it's decision time.

Ten days ago, he said the US was prepared to go to the "rescue" of Iranian protesters if their government used violence against them.

The US was, the president said, "locked and loaded and ready to go".

That was before the violent crackdown in Iran had really begun. Now, with its full extent being shockingly revealed, the world waits to see how Trump will respond.

"Nobody knows what President Trump is going to do except for President Trump," White House Press Secretary Karoline Leavitt said. "The world can keep waiting and guessing."

But for how long?

Senior officials are due to brief the president on Tuesday on possible courses of action. Speaking to reporters on Air Force One on Sunday, Trump said he was looking at "some very strong options".

Flushed with success in Venezuela - the president described the capture of Nicolas Maduro as one of the most successful operations in US history - the temptation to deploy the military must be considerable.