France said Thursday that a British exit from the European Union would be a tragedy, but warned that Britain’s demands for reform could not be met at any price.

France said Thursday that a British exit from the European Union would be a tragedy, but warned that Britain's demands for reform could not be met at any price.

British Prime Minister David Cameron has said he wants a deal on his EU reform demands by February so that he can campaign to stay in the bloc ahead of a referendum on membership, which he has promised to hold by the end of 2017.

A British EU exit would be "a very bad thing," French Prime Minister Manuel Valls told reporters at an annual gathering of billionaires and political leaders in the snow-blanketed Swiss ski resort of Davos, where discussions have turned to the specter of a so-called Brexit.

"There needs to be a deal, but not at any price," the French prime minister said.

"Anything that allows us to simplify the organization of Europe, yes. Anything that throws into doubt the foundations of the European project or the eurozone, no."

Valls' rather downbeat assessment contrasted with more positive noises from his German and Dutch counterparts in Davos on Thursday.

Cameron's most hotly contested proposal is a four-year ban on top-up benefits for EU migrants working in Britain, which critics say is discriminatory and threatens freedom of movement in the EU.

The British leader, who is to speak at Davos later in the day, also wants the EU to give Britain safeguards against more political integration, to protect countries that do not use the euro currency and to boost economic competitiveness.