Britain will push for a tightening of the diplomatic and economic "stranglehold" on Syria at a meeting of regional powers in Tunisia on Friday, Foreign Secretary William Hague said.
Hague said he would bring up the Syria issue on Thursday at talks on the sidelines of a major conference on the future of Somalia which is taking place in London.
"I will be discussing today with (US Secretary of State) Hillary Clinton and many of the Arab leaders what we can achieve at that meeting (in Tunisia). I think part of that has to be tightening a diplomatic and economic stranglehold on the Assad regime," he told the BBC.
Hague said the failure to stop President Bashar Al-Assad from killing civilians was a "deeply frustrating situation", but ruled out military action like the NATO-led offensive against Libya last year.
Military action against Syria would be "much more complicated and would have to be on a much greater scale than in Libya, so that's not something we're likely to embark on," Hague said.
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He said the international community had "supplied food rations and other emergency supplies" to Syrians affected by the violence.
"People have been dying in their thousands, that continues, the Assad regime continues to act seemingly with impunity," he said, a day after two western journalists were killed in shelling of the Syrian city of Homs.
"But I think we can agree a wider set of measures across a large group of nations, I think we can tighten the European Union sanctions on Syria when we meet on Monday."
He added: "Clearly the economic measures that we are adopting make the life much more difficult for the Assd regime. We have cut off a quarter of their revenues for instance by stopping all oil imports to Europe."
The "Friends of Syria" conference in Tunis will gather top diplomats from the Arab League, Europe and the United States, along with the opposition.
Russia has denounced the meeting as one-sided and refused to attend. China has also refused to commit itself.