The situation in Syria resembles Bosnia in the 1990s, Foreign Secretary William Hague said as he warned time was running out to stop the killings in the country.
Mr 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. What was needed was a united way forward, he said.
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."
He said the UK and Russia agreed that President Assad did not have to be in charge in 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.
But he said it would be hard to see how Iran could attend the conference, which is one of the demands of Russia, as it had already given Syria technical support and advised the regime how to suppress protests.