Britain has not ruled out any option to save lives in Syria, William Hague warned, as the regime’s interior ministry was reportedly hit by an explosion.
The Foreign Secretary said president Bashar al-Assad should not “doubt our resolve” to react strongly if the military escalate the conflict.
At a Friends of Syria meeting in Morocco, he urged more countries to rally behind the opposition and warned that time was short to secure transition.
France, which with the UK has already formally recognised Syrian National Coalition as the government-in-waiting, said more than 100 nations present had now followed suit.
The apparent breakthrough came after Mr Hague told the gathering he was “deeply disappointed by the failure of the international community” to put sufficient weight behind it.
“Syria needs a political transition leading to an inclusive new government, with full executive authority,” he said in his opening remarks.
“This is the course most likely to achieve stability in the country.
“But in the United Kingdom we do not rule out any option to save lives. The Assad regime should not doubt our resolve, or miscalculate how we would react to any use of chemical or biological weapons against the Syrian people.
“The next few months will determine whether a peaceful political transition can be agreed, or if Syria is to face more bloodshed.”
Mr Hague said the UK would add another £1 million in communication support to the £7 million of non-lethal help it has already supplied.
And he called on other countries to boost aid spending to ease the humanitarian crisis faced by half a million refugees and up to three million people displaced by the violence.
Mr Hague’s comments came before reports that a bomb hit the main entrance of Syria’s interior ministry.
Syria’s newly recognised opposition has meanwhile urged the USA to review its blacklisting of the jihadist group, the al-Nusra Front.
Earlier this week, President Barack Obama recognised the National Coalition as the legitimate representative of the nation’s people. It also blacklisted as a terrorist group the al-Qaeda-linked al-Nusra Front, which US officials fear seeks to hijack the revolution.
“The decision to blacklist one of the groups fighting the regime as a terrorist organisation must be re-examined,” the bloc’s leader, Ahmed Moaz al-Khatib, said at a meeting in Morocco of the Friends of Syria group that included the United States.
“We can have ideological and political differences with certain parties, but the revolutionaries all share the same goal: to overthrow the criminal regime” of President Bashar al-Assad.
Without naming al-Nusra, William Burns, the US deputy secretary of state, urged Mr al-Khatib’s coalition to “take a firm stand against extremists” who could commandeer the revolt.
“Transition is coming one way or another,” he told the meeting in the city of Marrakesh.
The decision to blacklist al-Nusra, an important fighting force in the uprising, has already triggered criticism from the powerful SyrianMuslim Brotherhood. A senior Brotherhood official said it was wrong and hasty.
“They are seen as (a group that) can be relied on to defend the country and the civilians against the regular army and Assad’s gangs,” Brotherhood deputy leader Farouq Tayfour told Reuters on Tuesday.
Mr al-Khatib said it was “no shame” if Syrian rebels were driven by religious motives to topple Assad. “Religion that does not liberate its people, and does not eliminate repression, is not authentic religion,” he said.
“The fact that the military movement is Islamic in its colour is generally positive. Jihad in the path of God, has long been a fundamental motivator for human rights.”
“We send a direct message to the Alawite brethren. The Syrian revolution is extending its hand to you, so extend your hand back and start civil disobedience against the regime because it repressed you like it repressed us,” he said.
Many Alawites, who have remained mostly loyal to Assad throughout the 20-month-old uprising in which more than 40,000 people have been killed, fear the rebels would exact brutal revenge on their community if they seize power.
But Mr al-Khatib, a Sunni Muslim former preacher at the ancient Umayyad mosque in Damascus, said the opposition coalition which he leads was committed to a pluralistic future “based on justice, equality and respect for human rights and preserving (Syria’s) unique social fabric”.
“This coalition … was born to restore hope and smiles of the Syrian people. Its objective is to bring down the Syrian regime and prepare for a national conference that will be inclusive and that will guide Syria towards the future.”