BRUSSELS, Belgium – The European Union’s commitment to further expansion, bringing in such countries as Turkey, was in doubt yesterday as a senior official admitted that the bloc was suffering from “enlargement blues.”

As E.U. leaders gathered in Brussels for a arguments over the budget and the constitution, it appeared that their summit could go down in history as the moment that Europe pulled up the drawbridge to its neighbors.

The French president, Jacques Chirac, sought to link the collapse of the E.U. constitution with hopes of admitting new members.

He questioned whether enlargement could continue in the wake of the “no” votes in France and the Netherlands. “In this new situation, can the union continue to expand without us having institutions capable of making this enlarged union function effectively?” he asked.

France’s ruling elite is largely convinced that the E.U. enlargement is a “British plot” to dilute the European project. To such figures, Britain’s role in putting the E.U. Constitution into suspended animation by putting a British referendum on hold, looks like just another step in that plot.

Mr. Chirac strongly hinted that France might yet have its revenge – turning the death of the constitution into a turning point for enlargement.

France originally led calls to create an E.U. constitution, saying that union institutions had to be reformed and decision-making streamlined to allow it to work with 25 member nations.

Mr. Chirac’s comments came a day after his newly appointed prime minister, Dominique de Villepin, questioned the policy of enlargement “in the absence of reformed institutions.”

The E.U. commissioner for enlargement, Olli Rehn, said that Europe was suffering from “enlargement blues.” The “no” votes in France and the Netherlands on the constitution carried a clear warning.

“We are concerned about the worries of our citizens, and therefore we have to be cautious regarding taking any new commitments in the field of enlargement,” he said.

At the same time, Mr. Rehn threw a lifeline to Turkey, which is due to start accession talks on October 3. “It is equally important to keep our existing commitments,” he said before the summit opened.

The E.U. has provisionally pledged to open membership talks with Turkey in October, and has signed deals with Romania and Bulgaria, which are due to join in 2007.

But the specter of Europe’s enlargement fatigue hung over the two-day summit.

Turkey’s accession is so sensitive that E.U. leaders have deleted any reference to the nation by name in draft conclusions to the summit prepared by foreign ministers earlier this week.

The original draft conclusions were to reiterate previous commitments to starting accession talks with Turkey and Croatia. However, France objected to any mention of the October start date for Turkish talks.

Rather than risk reopening the debate over Turkey, Luxembourg, which holds the union’s rotating presidency, opted for conclusions that call for the full implementation of accession decisions made to date – a method of referring to Turkey without using the “T-word.”

That move was supported by Britain, one of the leading backers of Turkish entry.

In Berlin, the opposition leader Angela Merkel, who is favorite to become chancellor after elections this September, told the German parliament that the E.U. should not hold full membership talks with Turkey.

It was clear that European citizens would never permit its entry, especially in countries such as France that had pledged to hold referendums on the subject of Turkish entry, she said.

“It would be totally irresponsible to negotiate with Turkey over 10 years, holding out the hope of full membership, in the knowledge that there will never be a majority for such a decision,” the Christian Democrat leader Mrs. Merkel said.

Mr. de Villepin said on Wednesday that it was clear that France’s “no” vote to the E.U. Constitution was linked to fears of future enlargement, and anger at the “rapidity” of recent accessions, which saw 10 new nations join last year, including former communist nations such as Poland, with their armies of low-paid, lowly regulated workers.

Mr. de Villepin said agreements to admit Romania and Bulgaria in 2007 should be kept. But he added: “Beyond that, we need to open a discussion with our partners, while respecting our current commitments, about the way to conduct future enlargements.”