David Cameron will chair a meeting of the National Security Council (NSC) to discuss possible military action against Syria.
Ahead of Thursday's recall of Parliament, the NSC is expected to discuss the intelligence gathered by United Nations inspectors from their visit to Mouadamiya, where last week's suspected chemical weapons attack is believed to have taken place. The council will also consider whether or not to push ahead with a military strike against President Bashar Assad.
Mr Cameron said before the meeting that any intervention in Syria would not be about the conflict itself, but preventing the use of chemical weapons by any regime.
Decisions about British involvement have not been taken, he said on Tuesday, adding Parliament was the "right place to set out all of the arguments". He said action must be "proportionate, have to be legal, would have to specifically be about deterring the use of chemical weapons".
Mr Cameron, whose request to recall Parliament early was granted by the Speaker, said Thursday's debate would ensure "proper" scrutiny and allow the Government to listen to MPs. "Obviously this is a developing situation, as I say, decisions have not been taken, but we shouldn't stand by when we see this massive use of chemical weapons and appalling levels of suffering," he said. "I think in Parliament is the right place to set out all of the arguments, all of the questions. But I would say this to people - there is never 100% certainty, there is never one piece or several pieces of intelligence that give you absolute certainty.
"But what we know is this regime has huge stocks of chemical weapons. We know they have used them on at least 10 occasions prior to this last widescale use. We know they have both the motive and the opportunity whereas the opposition does not have those things and the opposition's chance of having used chemical weapons in our view is vanishingly small."
The NSC includes Defence Secretary Philip Hammond, Home Secretary Theresa May and Deputy Prime Minister Nick Clegg among its members. Foreign Secretary William Hague has warned that Britain cannot allow the use of chemical weapons to go unchallenged, saying Britain "cannot allow diplomatic paralysis to be a shield" for Assad.
On Tuesday, Labour leader Ed Miliband indicated that his party would consider supporting international action, "but only on the basis that it was legal, that it was specifically limited to deterring the future use of chemical weapons, and that any actions contemplated had clear and achievable goals". Labour MP Diane Abbott said she may be forced to resign from the front bench if Mr Miliband supported intervention. Ms Abbott, the shadow health minister, told The Guardian she was opposed to British involvement based on the current available evidence. "I voted against the Iraq War. At the moment, I can't see anything that would make me vote for intervention in Syria," she said. "Essentially it's a civil war. What Libya and Egypt have taught us is that these situations in the Middle East are complex. It's not good guys in white hats and bad guys in black hats." Asked if she would resign her position if Labour supported military action, Ms Abbott said: "It would put me in a very difficult position."
While political momentum towards intervention mounts, the British public has yet to be persuaded. A YouGov survey for The Sun revealed that nearly three-quarters of people oppose the deployment of British troops to Syria, and a majority of 3-1 believe the Government should be bound by Parliament's vote.
Downing Street said Mr Cameron set out the options being considered by the UK in a telephone call to US president Barack Obama on Tuesday night. A No 10 spokesman said: "The PM spoke to President Obama last night to further discuss the serious response to last week's chemical weapons attack in Syria. Ahead of today's NSC, it was an opportunity for the PM to hear the latest US thinking on the issue and to set out the options being considered by the Government. Both leaders agreed that all the information available confirmed a chemical weapons attack had taken place, noting that even the Iranian president and Syrian regime had conceded this. And they both agreed they were in no doubt that the Assad regime was responsible. Regime forces were carrying out a military operation to regain that area from the opposition at the time, and there is no evidence that the opposition has the capability to deliver such a chemical weapons attack. The PM confirmed that the Government had not yet taken a decision on the specific nature of our response, but that it would be legal and specific to the chemical weapons attack."
