Europe's political crisis deepened yesterday with calls for EU enlargement to be slowed down following referendum defeats for the constitution and Saturday's failure to agree a new seven-year budget.
European Commission vice-president Günter Verheugen said the EU should exercise restraint in admitting new states.
Austrian chancellor Wolfgang Schüssel said fears over enlargement contributed to the rejection of the constitution in France and the Netherlands.
"There are other options apart from full membership of the European Union for achieving political and economic stability throughout Europe," Mr Verheugen told Bild am Sonntag newspaper.
He said membership talks with Turkey, due to start in October, would be open-ended in terms of their outcome, and it could be 10 years before it was clear if Turkey was actually heading for membership.
He said the accession of Bulgaria and Romania, which are due to join the EU in 2007, could be postponed if they were not ready.
Mr Schüssel told Der Standard newspaper that the EU should be more imaginative in its relationships with neighbouring countries.
"At the moment the only instrument we have is membership. Otherwise a country stays outside the door. That is inadequate."
The acrimonious collapse of negotiations on the EU budget on Saturday has exposed sharp divisions among European leaders over the future direction of the EU.
British prime minister Tony Blair will this week tell the European Parliament of his plan to begin a drive for economic reform in the EU during Britain's EU presidency, which starts on July 1st.
Most other leaders have blamed Mr Blair's refusal to accept a cut in Britain's budget rebate for the summit's failure, and there is little chance of a deal under the British presidency.
Negotiations will resume in earnest under Austria's presidency, during the first half of 2006.
At the end of the summit the leaders issued a declaration that abandoned the November 2006 deadline for ratifying the EU constitution to give more time for debate.
"This period of reflection will be used to enable a broad debate to take place in each of our countries, involving citizens, civil society, social partners, national parliaments and political parties.
"This debate, designed to generate interest, which is already under way in many member states, must be intensified and broadened," the declaration said.
The leaders agreed to assess the situation in early 2006, but the Taoiseach said that the Government would publish a White Paper on the constitution in September and seek to generate a broad debate about Europe.
"It has to be a period of active engagement rather than reflection, not just on the constitution but on Europe generally," he said.
The crisis over the constitution and the failure of last week's summit have already triggered a debate about the direction of the EU.
British foreign secretary Jack Straw said Europe was at a turning point, and had to face a fundamental choice.
"It's essentially a division between whether you want an EU that is able to cope with the future or whether you want an EU that is trapped in the past. It is not one that Europe can dodge."
Some EU leaders have accused Britain of seeking to abandon the process of political integration in Europe, and of attempting to reduce the EU to a free-trade zone.
Mr Schüssel said: "The British want a different Europe. They want more a market-oriented Europe, a large market, but no deeper union.
"Anyone who wants such a model leaves behind the European social and economic model which has served us well, which the citizens want and which has made us strong," he said.