Syria conflict: Cameron and Obama pledge to boost opposition
The US and the UK say they will work to strengthen the moderate opposition in Syria and create a transitional body to replace President Bashar al-Assad.
British Prime Minister David Cameron, in Washington for talks, said there was an "urgent window of opportunity before the worst fears are realised" in Syria.
Addressing reporters at a news conference, both Mr Cameron and US President Barack Obama also faced questions on domestic issues.
Jonny Dymond reports from Washington.