US President Barack Obama has approved arming the Syrian rebels for the first time, according to US officials.
The officials confirmed that the president has authorised sending weapons to opposition forces after the White House disclosed that the Assad regime had crossed "clear red lines" by deploying chemical weapons.
The move also came a day after it was reported that Bill Clinton said Obama risked looking like "a wuss and a fool" over his lack of intervention in Syria.
Three US officials confirmed the decision after Senator John McCain said he was told on Thursday that Obama was going to "provide arms to the rebels".
It is believed that the CIA are expected to train the Syrian rebels to use any weaponry the US provides.
The White House move has not changed the British position, a Downing Street spokesman confirmed on Thursday night.
The Obama administration has indicated it would further increase the "scope and scale" of assistance to opposition forces, including direct "military support".
But there was no immediate announcement of what that would comprise or the timescale for accelerating support.
The UK - along with France - has reported repeated small-scale incidents of apparent chemical weapon use by regime forces to the United Nations investigation team.
Both countries led a successful joint bid to lift an EU embargo on supplying arms to opposition forces although Prime Minister David Cameron stressed yesterday that no decision had been taken to arm the rebels.
He is due to hold talks with Russian president Vladimir Putin at Downing Street on Sunday as part of efforts to break the international deadlock.
The crisis will also be high on the agenda when they join other world leaders, including Mr Obama and French president Francois Hollande, at the G8 summit in Northern Ireland on Monday.
Foreign Secretary William Hague discussed the crisis - which the United Nations now believes has cost at least 93,000 lives - with US counterpart John Kerry on Wednesday.
He said after those talks that the international community must be "prepared to do more" to up the pressure on the regime.
The question of whether Western nations should step into help rebels fighting the Assad regime has been hotly contested.
Walid Safur, the British representative of the opposition Syrian National Coalition, said the rebels needed anti-aircraft and anti-tank missiles.
He provided assurances that any arms would not fall into the hands of extremist elements fighting with the opposition.
He told BBC Radio 4's Today programme: "We would like to see sophisticated weapons to bring down any aircraft and to deter this regime from bombarding the urban and civilian areas."
"We would like to see anti-aircraft missiles and anti-tank missiles in order to deter the Syrian regime.
"The Syrian regime is attacking any target, civilian targets, infrastructure targets, whatever. And now more than 50% of the infrastructure of Syria has been turned into rubble.
"Many people were obliged to desert their homes - we have more than seven million displaced inside Syria and around two million outside Syria, it's an unimaginable number, it's a massive and huge number."
He added: "Diplomacy has failed so far but however I would like to say that when weapons are given to the right hands it will not go into the wrong hands.
"It's not too chaotic, we know the geography on the ground and we can make sure that the weapons will not go into the wrong hands."
But Tory MP John Baron, a member of the Foreign Affairs Select Committee, said there were still questions over how to make sure extremists do not get any arms supplies.
"Furthermore, you throw more weapons in, it can only create more violence and suffering," he told Today.
"We must remember that Syria is a melting pot for a proxy war being fought out at various levels including Sunni versus Shia, the West versus China and Russia, minorities within the country such as Alawites and Christians against what could follow and indeed Iran versus Saudi Arabia.
"Pouring more weapons into the region would not only perhaps escalate the violence within Syria but beyond Syria's borders."
He said the solution to the conflict was a diplomatic and political one and urged David Cameron to allow a vote in Parliament on any British decision to send weapons.
"We in the UK do not have to follow the US. Good friends sometimes say to each other, look, you're making a mistake," he said.
"We have encouraged David Cameron to admit that this decision to arm the rebels or step up in any way UK support for the Syrian rebels will be subject to a debate and vote in Parliament."