By Alex Stevenson Follow @alex__stevenson
The prime minister appears unlikely to offer British voters a referendum on Europe if EU leaders push ahead with their plans for a treaty change.
Both French president Mr Sarkozy and German chancellor Angela Merkel have indicated their enthusiasm for greater fiscal integration within the eurozone ahead of next week's Brussels summit.
Britain is nervous that the establishment of a two-tier Europe could make it harder for non-euro EU member states to trade with eurozone countries.
"We're almost there," Ms Merkel told the German Bundestag this morning.
"Of course there are difficulties to be overcome, but the necessity of such action is widely recognised.
"We're not just talking about a fiscal union but starting to create one. I believe you can't overestimate the importance of this step."
Mr Sarkozy said the Maastricht Treaty was "imperfect" and said the eurozone would break up if steps towards "economic convergence" were not taken.
Chancellor George Osborne has repeatedly called for greater fiscal integration in the eurozone, but the move poses a political headache for Mr Cameron.
Any treaty change would require the public have their say thanks to the coalition's 'referendum lock', however.
The prime minister may seek to deny the public a vote, despite a massive rebellion by 81 Conservative backbenchers on the issue in October, by arguing that the treaty changes are only minor alterations.
"When you look at the crisis in the eurozone, the real need there is for the institutions of the eurozone to get behind the currency to convince the markets they have the firepower to do that.... the second fundamental thing is real competitiveness throughout the eurozone so the eurozone works properly," Mr Cameron said after meeting with Mr Sarkozy in Paris today.
"Neither of those things actually require treaty change. I'm very clear if there is treaty change I will make sure we further protect and enhance Britain's interests, but we'll see what happens next Friday.
"The bottom line for me is what is in the interests of the UK, and how can I promote and defend that."