Europe's foreign ministers have rallied round the embattled French campaign for the European constitution, arguing that a No vote on the May 29 referendum would set back the European Union's drive to play a bigger part on the world stage.

Many officials fear that a French rejection, which could prove terminal for the constitutional treaty, would also halt the EU's enlargement drive - sometimes dubbed "the most successful foreign policy in the world". It could also kill reforms intended to boost the EU's diplomatic clout, such as the creation of an EU foreign minister and a new external action service.