David Cameron will hold talks with ministers and senior officials over the spiralling situation in Syria.
The Prime Minister is to chair a National Security Council (NSC) discussion of military, humanitarian and diplomatic options for stemming the bloodshed and growing refugee crisis.
The meeting comes after Mr Cameron visited a UN-run compound on the border with Jordan last week and saw the conditions being endured by tens of thousands of fleeing Syrians.
He said he was determined to do "more" and would be working with newly re-elected US president Barack Obama to up the pressure on Bashar Assad's regime. "Frankly, what we've done so far is not working," he said.
The measures under consideration are thought to include a no-fly zone, supplying weapons to rebel forces, and encouraging other countries in the region to provide arms.
Syrian opposition leaders are due in London on Friday for talks, amid renewed efforts to create a unified alternative to Assad.
This week France became the first Western power to accept the opposition coalition as the legitimate government-in-exile.
The US and the UK have both signalled support but stopped short of formal recognition.
Some 30,000 people are believed to have died as a result of the the conflict so far. The Syrian Arab Red Crescent has also estimated that 2.5 million people have been displaced within the country.
The escalating violence in Gaza is not formally on the agenda for the NSC, but ministers and officials are expected to discuss it as part of the wider context.