By Alex Stevenson Follow @alex__stevenson
Britain will help tighten the international "stranglehold" on Bashar al-Assad's regime, William Hague has pledged, as violence continues in Syria.
The foreign secretary admitted the situation was "deeply frustrating" a day after Sunday Times journalist Marie Colvin and 60 other civilians were killed in Homs - the 19th consecutive day the city has been attacked by Assad's military.
But Mr Hague said Syria's strong military, its sensitive position in the region and a lack of international backing from the UN all stood in the way of a military intervention in Syria.
He will discuss the situation with US secretary of state Hillary Clinton and Arab leaders ahead of tomorrow's Friends of Syria summit in Tunisia, which 60 countries will attend. Russia and China, which vetoed a UN resolution criticising Damascus, will not be present.
Next Monday EU ministers are expected to approve tightened sanctions against Syria. Mr Hague said he hoped to secure "a wider set of measures" than those already in place.
"We want Assad to go," he told the Today programme this morning.
"Clearly the economic measures make life much more difficult for the Assad regime. We have cut off a quarter of their revenue by stopping all oil imports into Europe.
"Are we militarily intervening without the authority of the United Nations? No, clearly we are not doing that."
Yesterday the Syrian ambassador was summoned to the Foreign Office to hear its political director explain that the British government is "horrified by the continuing unacceptable violence in Homs".
Over 6,200 people have been killed in the past ten months, but Syria's 325,000-strong military is preventing a repeat of last year's international intervention in Libya.
The use of force against Syria would have to be on a "vastly greater scale" than that used to topple Muammar Gaddafi, Mr Hague said. He added: "The consequences of any outside intervention are much more difficult to foresee."