After US president Barack Obama's speech on Thursday, in which he said that Syrian president Bashar al-Assad must lead a political transition or "get out of the way", US Secretary of State Hillary Clinton has also made some strong statements about Syria.

"Unfortunately, the evidence thus far is that he's not providing the kind of leadership that is needed," she said in an interview with US television station CBS.

Clinton stopped short of saying that al-Assad must step down.

"It would be better if the people of Syria themselves made it clear to Assad that there have to be changes," she said.

In his speech on Thursday, Obama said: "President Assad now has a choice. He can lead that transition or get out of the way. The Syrian government must stop shooting demonstrators and allow peaceful protests."