‘Hezbollah and Iran are supporting Syrian leader’

“This is a regime that is increasingly dependent on external support. The regime is being propped up by others outside, further undermining its legitimacy. It also shows that is a crisis that is increasing the threat to regional stability.”

Speaking ahead of a meeting of the Friends of Syria alliance in the Jordanian capital, Amman, Mr Hague said Britain would urge world powers to set a date in the next few days for an international conference to try to end the two-year conflict.

He said: “It is important that it takes place as quickly as possible because people are dying and more and more people are driven from their homes. The risk to regional stability grows every day so this something that cannot be debated endlessly.”

His comments echo those of an EU diplomatic source, speaking late on Tuesday.

The source, also attending the Amman meeting, said: “Since November the regime has been able to go on the offensive not because it is stronger, but because those backing it – Iran, Russia, Hezbollah – are directly helping it either through weapons, planning of operations or financial assistance.”

Mr Assad and his supporters would be mistaken if they believed they could resolve the crisis by a military defeat of their opponents, Mr Hague said.

He added: “They need a political solution whatever the circumstances on the ground … Their country is collapsing.”