The situation in Syria resembles Bosnia in the 1990s, Foreign Secretary William Hague said, warning that time was running out to stop the brutal violence.
Hague said it was now up to Russia to use its leverage with President Bashar Assad's regime to bring an end to the brutal violence in Syria.
He told Dermot Murnaghan on Sky News the continued political and trade isolation of Syria was the second best option. A "united" way forward was needed, he claimed.
Asked whether the government had ruled out military intervention, Mr Hague said: "I think we don't know how things are going to develop. Syria is, as I said in the last couple of weeks, on the edge of a collapse or of a sectarian civil war so I don't think we can rule anything out.
"But it is not so much like Libya last year, where of course we had a successful intervention to save lives.
"It is looking more like Bosnia in the 1990s, being on the edge of a sectarian conflict in which neighbouring villages are attacking and killing each other so I don't think we can rule anything out.
"But it does mean ... there is an increasing commonality of analysis with Russia. The Russians are concerned about that scenario."
Taken from a video posted on the Facebook page for the Activists News Association this shows some of the bodies after the massacre. This has not been independently verified
Russian Foreign Minister Sergey Lavrov has said that it will no longer stand in the way of Assad's departure, reported The Guardian.
"If the Syrians agree [on Assad's departure] between each other, we will only be happy to support such a solution," he said. "But … it is unacceptable to impose the conditions for such a dialogue from outside."
Hague told Sky News that while the UK and Russia agreed President Assad did not have to continue as President of Syria but a way forward could not be found while the violence continued. Russia now had to use its "leverage" to ensure the Syrian regime ended the violence, he added.
Mr Hague said he "welcomed in principle" the Russian proposal for an international conference on Syria, but warned it must "lead to a change and not just buy time for the regime to kill more people".
He said the way forward was to adopt the peace plan of former United Nations secretary-general Kofi Annan.
Kofi Annan spoke frankly at the New York meeting on Thursday, at which 193 states were present
Annan urged the UN to unite behind efforts to end the Syrian conflict on Friday and called for "consequences" if his peace plan was not implemented, blaming its failure on President Bashar Assad's government.
He told the security council on Friday: "Clearly, the time has come to determine what more can be done to secure implementation of the plan.
"We must also chart a clearer course for a peaceful transition, if we are to help the government and opposition, as well as Syrian society, to help resolve the crisis" he added.
David Cameron has condemned the attacks, which is one of the bloodiest in the 15-month uprising against Assad
The British Government has already provided £8.5 million towards helping alleviate the "appalling" humanitarian situation. However Hague continues to stress the need for international unity.
Mr Hague added: "Of course, we will keep talking to the Russians about how we can do this.
"Every other solution to the Syrian crisis involves a lot more death.
"If we had international agreement insisting on the Annan plan being implemented then there would access to the whole of Syria for monitors who are currently being shot at by supporters of the regime, to monitor the ceasefire, armed forces would be pulled back from populated areas in Syria, a political process in which Syrians can decide their own future can begin and there would be access to the whole country for aid agencies.
"What if the Annan plan fails completely because clearly time is now running short? In the meantime we have to continue to try and find a united position with Russia on the way forward.
"If all of that fails then of course we will be returning to the (United Nations) Security Council for further measures, we will be asking all the countries in the Friends of Syria to step up the isolation of the regime, we will be greatly increasing our support for the opposition.
"But all of that would be second best to an agreed way forward."