The leaders, meeting here for two days, will confirm the partial suspension of membership talks with Turkey, whose rocky path toward Europe's rich club has embodied the concerns and fears about the ability to take on new members.

Over their evening meal, the 25 heads of state and government will lay out their visions for enlargement after the bloc welcomes in Bulgaria and Romania as the 26 and 27th members on January 1.

"The aim is to confirm a common understanding on the future of the enlargement process," Finnish Prime Minister Matti Vanhanen, hosting the summit as EU president, said in an invitation to his fellow leaders.

Before dinner, Vanhanen will present an analysis on the constitution, which was meant to help the EU run more smoothly as it grows, until it was rejected by French and Dutch voters in referendums last year.

Enlargement fatigue setting in

Those votes, due in part to fears of "enlargement fatigue" and the idea of a large, relatively poor and mainly Muslim country like Turkey joining, sent the Union spiraling into its worst ever crisis.

An EU official said that "the level of ambition is weak" at the moment on enlargement, as the member countries know that any concrete proposals could be put on the back burner until the EU's "institutional" house is put in order.

In any case, the leaders are expected to concede that the impasse over the constitution must end before new members are considered beyond Bulgaria and Romania.

The German EU presidency, starting on January 1, is expected to take forward the process, with no real decisions expected before France takes over the helm in the second half of 2008.

However, a study released Thursday suggested that it would be in Germany's interest to promote further enlargement.

According to a study commissioned by the German Economy Ministry, Germany, the eurozone's largest economy, had already largely profited from the extension of the EU from 15 to 25 nations in May 2004. The study said that enlargement had boosted Germany's gross domestic product (GDP) by around one percentage point, and that the benefits would continue as the bloc expands further.

Germans plan to revive constitution

In regard to the EU constitution, German Chancellor Angela Merkel said Thursday that it would be a "historical failure" if agreement on a constitutional treaty was not struck before European elections in 2009.

The chancellor said that she and the German government would work "intensively" during the six-month presidency "so that such a treaty, based on our common values, can go into force."

Whatever the outcome here, the leaders' stance will have major repercussions for Turkey, which began membership talks last year, but also for EU candidates like Croatia and Macedonia and other hopefuls in the Balkans.

British Prime Minister Tony Blair, a strong supporter of Ankara's candidacy, is expected to travel to Ankara after the summit ends on Friday in a gesture of solidarity.

Other points of order include the increasingly high-profile issue of sustainable energy supply, but the real initiatives on that subject are also expected to be taken by Germany.

Serbia creeps up EU agenda

With Turkey resolved for now and nobody keen to wade too far into the issue of institutional reform, one other issue is looming as a possible bone of contention, in what is likely to be a quiet and short summit, that of Serbia.

The EU froze in May a Stabilization and Association Agreement -- a first step toward joining the EU -- over Serbia's failure to hand over former Bosnian Serb military chief Ratko Mladic to the UN war crimes court.

Italian Prime Minister Romano Prodi is expected to ask his counterparts to lift the EU's condition of full cooperation with the court for the talks with Belgrade to resume.

But Britain and others oppose this idea and most would prefer to reassess ties with Belgrade, and the situation in the breakaway province of Kosovo, after Serbia's January elections.