Downing Street has said "nothing is off the table" including arming the rebels or imposing a no-fly zone when it comes to dealing with the Syrian regime, after the United States decided to deliver weapons to the anti-Assad forces.
On Friday morning a spokesperson for David Cameron said the the British government welcomed the "candid assessment" by the Obama administration that the Syrian regime had used of chemical weapons.
No.10 said British intelligence agencies have presented evidence of the use of chemical weapons in Syria to allies and to the United Nations.
Asked whether the UK would consider joining the Americans in arming the rebels or taking part in a no-fly-zone, the spokesperson said: "This is a complex problem, the use of chemical weapons goes against all international laws and norms. We are discussing it as a matter of urgency with our colleagues across the international community, but no decision has yet been taken."
The spokesperson added: "Nothing is off the table, but clearly there are important discussions now ongoing."
Cameron is due to hold a phone conversation with president Obama later today. He will also hold talks with Russian president Vladimir Putin over the weekend.
William Hague said the situation demanded "a strong, determined and coordinated response from the international community".
"We have to be prepared to do more to save lives, to pressure the Assad regime to negotiate seriously, to prevent the growth of extremism and terrorism, and to stop the regime using chemical weapons against its people," he said.
On Thursday President Obama approved arming the Syrian rebels for the first time. US administration 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.
Last month, Britain and France succeeded in lifting the European Union arms embargo - allowing London and Paris to arm rebel forces if they so wished.
However Cameron faces severe opposition to such a move in parliament, including on his own backbenches.
Last week 81 Conservative MPs wrote to Cameron to demand the Commons be given a vote before any arms are delivered to Syrian rebels.
The prime minister has said MPs will "have a say" on what happens. But many MPs are not convinced by the pledge. They have asked for a guarantee any debate and vote will happen before action is taken - rather than after the fact.
It is also far from certain that Cameron would win any vote in the Commons. The Labour Party has expressed serious doubts about delivering weapons to the region and Nick Clegg is said to be leading opposition within cabinet to the plan on behalf of the Lib Dems.
Tory opponents of arming the rebels believe a significant proportion of the parliamentary Conservative Party is also opposed.
John Baron, a member of the foreign affairs committee, recently told HuffPost UK his Conservative colleagues had "severe reservations" about the idea.
And speaking on BBC Radio 4's Today programme this morning, Baron said: "Pouring more weapons into the region would not only perhaps escalate the violence within Syria but beyond Syria's borders."
"We in the UK do not have to follow the US. Good friends sometimes say to each other, look, you're making a mistake."