The US Secretary of State John Kerry said the continued violence in Syria showed that it was time for President Bashar al-Assad to go.
Speaking alongside Kerry, Foreign Secretary William Hague called for support for Syria's opposition to be increased significantly to bring the conflict to an end.
More top news
Police have released 12 images of people wanted in connection with what they describe as 'disorder' at a McDonalds in central London.
Sunderland have appointed former Manchester United manager David Moyes to replace new England boss Sam Allardyce
A Russian adventurer looks to have smashed the record for a solo round-the-world flight in a hot air balloon.