Britain hopes to decide within days whether to recognise the new Syrian opposition coalition as the legitimate voice of the country's people.
British Foreign Secretary William Hague said that the creation of a coalition of forces opposed to President Bashar al-Assad was "a big step forward".
He stressed that he would need more information about their plans before deciding whether the UK should recognise them.
Mr Hague will urge the group to develop a clear plan for political transition in Syria when he opens talks in London, which are being hosted by the UK's special envoy, Jon Wilks.
He will also press for the need to respect human rights and "win over the middle ground of opinion" in the nation amid the spiralling violence.
The US and the UK have signalled support for the group but stopped short of the formal recognition of it as a government-in-waiting already accorded by France.
Mr Hague said that Britain's position remains that it will not provide arms to the Syrian opposition.
He said he will discuss the possibility of providing more non-lethal assistance.
The UK hopes to have talks soon with European partners on the future of the EU arms embargo.
Britain's Prime Minister David Cameron chaired yesterday's National Security Council (NSC) discussions between ministers and officials on military, humanitarian and diplomatic options for halting the violence and refugee crisis.
He last week ordered all options, including arming rebel forces opposed to President Assad, to be put back on the table amid frustration at international failure to curb the bloodshed.
Among controversial strategies being considered by Mr Cameron is allowing Mr Assad a safe passage out of Syria even if that means he evades international justice.
Downing Street said the hour-long NSC meeting involved "a thorough discussion of the full range of options" - military as well as political and diplomatic.
British officials are also examining the terms of the EU embargo, which prevents the UK directly supplying the rebels with arms for ways to justify such a move.
Mr Cameron said last week, after visiting a refugee camp in Jordan, that he would make the crisis a top priority in working with the US during Barack Obama's second term.