David Cameron: World uniting to fight 'evil threat' of IS
David Cameron has said the "world is coming together" to fight so-called Islamic State as he held talks with French President Francois Hollande.
Speaking in Paris, the prime minister said it was his "firm conviction' that the UK should join air strikes in Syria but the decision would be up to MPs.
He said he would set out his case to Parliament this week ahead of a vote expected before Christmas.
The UK is making its Akrotiri airbase in Cyprus available to the French.
As France pushes for a stronger international coalition against IS in the wake of the terror attacks in Paris, which have left 130 people dead, the French President said his country would "intensify" its action in Syria.
IS has also claimed recent attacks in Tunisia, Egypt, Beirut and Turkey among others.
Mr Cameron said Friday's unanimously passed UN Security Council resolution, which pledged the international community to "redouble" action against IS, showed the unity there now was in the fight against violent jihadists in Europe and around the world.
"We have shown our firm resolve and together we will destroy this evil threat," he said.
Currently, the RAF are only able to bomb such targets in Iraq, after MPs voted in 2013 to not allow bombings to take place in Syria. But they did later approve British air strikes against IS extremists in Iraq.
Mr Cameron is preparing to set out his plan for tackling the ongoing crisis in Syria this week, coming after a Foreign Affairs Committee report said the UK should not join allied bombing in Syria without a coherent international strategy on IS.
"I firmly support the action that President Hollande has taken to strike Isil in Syria and it is my firm conviction that Britain should do so too," he said. "Of course that will be a decision for Parliament to make."
Speaking later after arriving back in the UK, Mr Cameron said it was in the UK's national interest "that we degrade and destroy this dreadful organisation", using every resource available - military as well as diplomatic, political and humanitarian.
The BBC's assistant political editor Norman Smith said he expected events to move fast, with Downing Street pushing for a vote on military action as early as next week if it was confident of victory.
Speaking on Monday, Defence Secretary Michael Fallon said ministers would be setting out the moral as well as military case for action.
"Understandably MPs want to be sure that there is a political track to this as well, that we are working with everyone in the region to create a more comprehensive, moderate government in Syria that will bring long-term security after the striking has finished."
But Professor Malcolm Chalmers, from the Royal United Services Institute, told the BBC that while there was no shortage of countries bombing targets in Syria there was a "shortage of targets that can be hit without obvious risk of collateral damage".
While up to 20 Tory MPs are thought still to oppose military intervention, a similar number of Labour MPs have said they will back action while others have said they will listen to the case put forward by the government before deciding.
Shadow defence minister Maria Eagle told the BBC: "We don't know what the prime minister is going to come up with yet... as long as MPs can see a plan that's supported by all, there is a chance we can agree on a proper way forward.
"We need to see the plan that the world comes up with will work before we decide how to vote and how the Labour party will whip its MPs."
Meanwhile, Mr Hollande will meet US President Barack Obama in the White House on Tuesday, to further discuss bolstering the international effort against IS. The French president then goes to Russia for similar talks with President Vladimir Putin.