BBC News with Fiona MacDonald

A key European Union summit on saving the euro currency is underway in Brussels. Shortly before it began, the leaders of France and Germany made dramatic appeals for support. President Nicolas Sarkozy of France warned that the risk of disintegration in Europe had never been greater. The German Chancellor Angela Merkel said changes to the European constitution were necessary to tighten fiscal discipline.

The president of the European Commission, Jose Manuel Barroso, said if a deal on much stricter rules to govern the eurozone was to emerge, then everyone had to play a part.

"What I expect from all heads of state and government is that they don't come saying what they cannot do but what they will do for Europe.

All the world is watching us, and what the world attains from us is not more national problems but European solutions." Our correspondent in Brussels Chris Morris says reaching agreement at the summit will not be easy.