Nicolas Sarkozy, the French president, and Angela Merkel, the German chancellor, will today present fellow European leaders with a proposal for a Mediterranean Union that leaves unanswered sensitive questions about how the scheme would operate.

According to a FrancoGerman document obtained by the Financial Times, the Mediterranean Union will seek to strengthen cooperation among the European Union's 27 member states and non-EU, mainly Muslim, countries in north Africa and the Middle East.

But the document is vague about what projects the Mediterranean Union would support and how they would be financed, indicating that final agreement is lacking on a subject that has caused much discomfort in Berlin about French intentions.

Mr Sarkozy and Ms Merkel are expected to unveil their initiative at a dinner tonight for EU heads of state and government at a two-day summit in Brussels. According to their joint document, the union would give fresh impetus to the so-called Barcelona process, which started in 1995.

The existing process is, in essence, a patchwork of overlapping economic, political and social agreements between the EU and 10 countries on the shores of the Mediterranean, from Morocco to Turkey.

Funds allocated to the Barcelona process could be used for Mediterranean Union projects, the document says. But "additionally and outside the EU budget" other money, including private sector finance, would be available.

Diplomats said this formulation addressed the concerns of Germany and other northern EU countries that, as the EU budget's biggest contributors, they would pick up the bill for projects managed by an institution over which they might have little or no say.

However, the document's wording leaves it uncertain exactly where funds not originating from the EU budget would come from.

In contrast to France's original plan to launch the Mediterranean Union at a grand summit on July 13-14, the document foresees a one-day summit of all 27 EU states and non-EU Mediterranean states on July 13.

As for possible Mediterranean Union projects, France distributed a paper to its EU partners in January that suggested initiatives in agriculture, energy, the environment, migration, transport and 10 other areas. None is mentioned in the Franco-German document.

It says the Mediterranean Union should have a copresidency, shared at the outset by one non-EU state and one EU state with a Mediterranean coastline.

When Mr Sarkozy first proposed a Mediterranean Union last year, it was quickly apparent that it was an Elysée palace initiative that lacked enthusiastic support from France's foreign ministry, which is deeply committed to the Franco-German relationship.