Paris, France (BBN)-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, reports BBC.
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.
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.
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. Of course that will be a decision for Parliament to make."
'POLITICAL TRACK'
Defence Secretary Michael Fallon, who is to brief Labour MPs next Wednesday, would not be drawn on when MPs would be asked to vote but said the UK's military capability - such as the use of Brimstone missiles - would be an important contribution to the international fight against extremists.
"We have to make our case," he told BBC Radio 4's Today.
"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 we will also be setting out the moral case that we have French aircraft, American aircraft, Australian aircraft coming half way around the globe and we can't let them take all the burden and all the risk of fighting Islamic State on our behalf."
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."
She added: "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."
The prime minister will appear in the House of Commons in the coming week to set out a "full-spectrum" strategy - including military, counter-terrorism and humanitarian actions.
Meanwhile, 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.
BBN/SK/AD