In a live Twitter chat with members of the public, Mr Hague admitted that the peace mission led by Kofi Annan, the former United Nations Secretary General, had “failed so far.”
And while he still wanted the plan, which has the backing of the UN Security Council including Russia and China, to succeed, Britain was prepared to take alternative measures if this proved impossible.
Moscow and Beijing have proved reluctant to agree to severe sanctions or military measures against Syria over the course of the 16 month conflict.
Russia in particular is a long-time ally of the Assad regime, and both nations are reluctant to agree to formal action after complaining that they felt duped by the passing of a UN Resolution which ultimately resulted in the ousting of Muammar Gaddafi, the Libyan dictator, last year.
Mr Hague suggested that unless the bloodshed in Syria ceased, the Government would seek a new UN Security Council Resolution (UNSCR) even without the backing of Russia and China.
He said: “Our strong preference is to work with Russia & China but if Annan plan fails no option is ruled out.
“We’re working with them. We support stronger action by Friends of Syria. If no progress made will seek strong UNSCR.”
Asked by a number of Tweeters why Britain did not seek a military resolution to the conflict in order to stop the bloodshed, he disclosed that while his preference was for diplomatic measures, an armed force had not been ruled out.
Mr Hague said: “Sustainable UN presence requires cessation of violence. No option is ruled out. But military intervention wld [sic] require international agreement and very large scale force.”
One Twitter user, Viresh Joshi, asked: “How many more massacres will it take until the global community realises that the Annan Peace Plan hasn’t worked?”
Mr Hague responded: “Hasn’t worked so far but best way of avoiding more massacres is to do everything we can to support peaceful transition.”
A new UN Resolution would likely be similar to the Chapter 7 resolution which was used to remove Gaddafi.
In the first place it would rule out military action, and instead threaten the: “complete or partial interruption of economic relations and of rail, sea, air, postal, telegraphic, radio and other means of communication.”
However, Mr Hague’s words in the Twitter chat make clear that Britain would be prepare to move on to an armed force as a last resort.
He was responding to Tweeters including one called “Noor,” who said: “The struggle has been going on for 16 months, when will the international community deem it necessary to intervene?”
Tweeter Khalil Agha asked: “How longer would u wait for Russia and China to support any fair solution in Syria. Average of killed civilians raised to 80 daily.”