Turkey finally began talks on joining the European Union in October 2005, more than 40 years after it first began to woo the emerging bloc.
Turkey is unlikely to join the EU for at least 15 years
But little more than a year later, the EU suspended the talks in eight out of the total of 35 policy areas.
What precisely is the problem? More generally, what are the main arguments for and against Turkish membership of the EU, and how does the accession process work?
Why is Turkey's EU membership bid in trouble?
There are two issues.
The European Union says Turkey must open its ports and airports to traffic from EU member Cyprus. Turkey says it will not do this until the EU takes steps to end the Turkish Cypriot community's economic isolation.
1959 - Turkey applies for associate membership of EEC
1963 - Association agreement with EEC is signed
1987 - Application for full EEC membership
1995 - Final agreement on EU-Turkey customs union
1999 - Turkey officially becomes EU candidate
2005 - Formal opening of accession negotiations
The EU also says that Turkey's efforts to bring its laws into line with European standards have slowed down. It has especially called on Turkey to repeal a law which it says undermines freedom of speech.
What effect is this having on the progress of Turkey's entry talks?
The EU has decided to suspend the talks in eight policy areas, known as chapters. It has also decided that none of the other 27 chapters can be signed off until Turkey opens its ports and airports to Cypriot ships and aircraft.
Will Turkey ever, in fact, join the EU?
Until recently EU officials talked about possible Turkish membership in 10 to 15 years. Recently European Commission President Jose Manuel Barroso used the phrase "15 to 20 years".
Some EU states are keen to ensure that Turkey does not feel that the door is being slammed in its face, and that membership remains a real possibility in future.
Other member states have always been rather cool about the idea of Turkish membership.
If Turkey does everything it is asked to, is membership a certainty?
No. The EU describes the negotiations as "an open-ended process, the outcome of which cannot be guaranteed beforehand".
Also, France and Austria have said they will hold referendums on whether to ratify Turkey's accession treaty, if the membership talks ever reach a successful conclusion.
Will Turkey budge on the issue of opening its ports to Cypriot ships?
It says it will not, unless the EU fulfils a commitment to end the isolation of the Turkish Cypriot community. The European Commission has drafted legislation that would allow direct trade between the EU and the Turkish Cypriots - but Cyprus, an EU member since 2004, will not agree to this.
The EU's Finnish presidency tried and failed to find a way of ending the deadlock. EU foreign ministers will return to the question of ending the Turkish Cypriots' isolation in January or February 2007.
What are the arguments against Turkish membership?
A range of arguments can be heard inside the EU. One is that Turkey is not culturally "European".
Another is that it will cause a wave of Turkish immigrants. A third is that widening the EU to include Turkey will prevent further deepening of political and economic union. A fourth is that Turkey is too big, and will therefore exercise too much power within the EU. A fifth is that it is too poor, and will cost the rest of the EU too much.
The former president of the European Commission, Jacques Delors, once said that the EU was a "Christian club". That view continues to be held in some European Christian Democrat parties.
In Turkey, there is some impatience with the EU's demands for reform, and fear that its insistence on minority rights for the Kurds will cause the country to break up.
What are the arguments in favour of Turkish membership?
One of the main arguments is that it will help forge a bond between the West and the Muslim world, and help Turkey spread stability in the volatile region beyond its eastern and southern borders.
Another is that Turkey's young and increasingly well-educated population can help the EU cope with the problems of an ageing population.
For Turkey, one of the attractions is a further step in its journey of modernisation, which the foundation of the Turkish Republic began. Membership of the EU's single market is a big incentive, as well as the freedom to travel or work in other countries, without applying for a visa.
For the Kurds, who make up 20% of the population, EU membership is a guarantee against discrimination.
Will Turkey's refusal to recognise Cyprus be a problem?
It could soon become a problem.
For the moment the European Union is focusing on fulfilment of Turkey's promise to open its ports and airports to Cypriot traffic.
However, a declaration issued by EU member states in September 2005 says that Turkey must recognise Cyprus before it becomes a member of the EU, and calls on Turkey to normalise relations with all EU member states.
Which countries are in favour of Turkish membership and which are against?
Cyprus, France, Austria and Denmark are distinctly cool about Turkish membership. Germany's governing Christian Democratic Union also thinks that Turkey should be offered a "privileged partnership" rather than full membership.
The UK, the Scandinavian countries and the states which joined the EU in 2004 are broadly in favour of Turkey's candidacy.
Who took the decision to start entry talks with Turkey?
The key decisions have been taken by leaders of the 25 EU member states. At a summit in Copenhagen in 2002 they promised to open talks "without delay", provided Turkey made sufficient progress on democracy, human rights and legal reforms.
The European Commission published a progress report in 2004, which gave Turkey the thumbs up. Then, in December 2004, the 25 EU leaders said the talks should begin on 3 October 2005.
This deadline was met, just about, when the foreign ministers of all 25 EU states reached a last-minute agreement on a text setting a framework for the negotiations on the evening of 3 October.
What was the problem that almost prevented agreement?
Austria prolonged the negotiations for two reasons. First, it wanted the framework to explicitly mention the possibility that the talks could result in "privileged partnership" rather than full membership. Second, it wanted an explicit mention of the limits to the EU's capacity to absorb new members.
The text finally agreed preserves the original wording that "the shared objective of the negotiations is accession."
But it adds: "While having full regard to all (EU political criteria), including the absorption capacity of the Union, if Turkey is not in a position to assume in full all the obligations of membership it must be ensured that Turkey is fully anchored in the European structures through the strongest possible bond."