The 11th-hour crisis session was called after Austria blocked agreement at a meeting in Brussels yesterday. Foreign ministers will now meet in Luxembourg, literally hours before the scheduled start of historic negotiations with Ankara.
The impasse presents a serious challenge to the British Government, which holds the EU presidency and is a firm supporter of Turkey's EU membership.
With a mainly Muslim population of 70 million, and with its relative poverty, the admission of Turkey would be the most ambitious enlargement to be undertaken by the EU. European governments agreed last year to open negotiations on 3 October, but the referendum "no" votes in France and the Netherlands have changed the political climate. The prospect of Turkey joining the EU figured in both campaigns amid growing signs of "enlargement fatigue".
Austria, the leading critic of Turkish accession, is isolated in holding out against a text that will serve as the basis for negotiation, and most diplomats believe that Vienna will not ultimately veto the start of talks.
In an interview with The International Herald Tribune, Wolfgang Schüssel, the Austrian Chancellor, avoided any direct threat to do so. But Vienna seems determined to extract a firm date for EU membership negotiations with Croatia, which it supports, in exchange for allowing the start of talks with Turkey.Austria's ambassador to the EU stuck to his government's insistence on an explicit reference to an alternative to full EU membership for Turkey, should the negotiations, which may last a decade, be unsuccessful.
The brinkmanship from Vienna is uncomfortable for the UK, which knows it cannot invite Abdullah Gul, the Turkish Foreign Minister, to the meeting in Luxembourg unless all 25 EU countries agree. Leaving him waiting at an airport to hear the EU's verdict before boarding a plane would also prove a humiliation.
Mr Gul said there were "serious problems" to resolve before negotiations could start and that there were conditions that Turkey could never accept.
Diplomats said that Austria has failed to circulate a clear text of its demands. However, the government in Vienna has pressed for changes to a passage saying the "shared objective of the negotiations is accession". The Austrians wish to see a reference to another type of relationship with the EU, though they do not insist on a reference to the term "privileged partnership". That is politically unacceptable to Ankara.
Turkey's membership bid is backed by none of the major political parties in Austria. Tensions are running high ahead of regional elections on Sunday.
The government in Zagreb is accused of failing to co-operate with the UN war crimes tribunal in The Hague, which has indicted a former Croatian general, Ante Gotovina. The UN's chief war crimes prosecutor, Carla Del Ponte, visits the country today before delivering a verdict on Zagreb's co-operation. Diplomats expect that it will record significant progress, and this might be enough to set a date for its membership talks to begin.
Meanwhile Recep Tayyip Erdogan, the Turkish Prime Minister, said that "if the EU is not a Christian club, this has to be proven". He said: "What do you gain by adding 99 per cent Muslim Turkey to the EU? You gain a bridge between the EU and the 1.5 billion-strong Islamic world. An alliance of civilisations will start."