Is Europe losing Turkey? New tensions threaten to harm a strategic bond that has long been seen as vital to the West's security.
Turkey became a member of the Nato alliance before Germany, and remains a bastion of stability in a region marked by undemocratic regimes and plagued by conflicts.
Turkish membership would show the EU was not just a Christian club
But a year-end deadline for Turkey to make important concessions in its talks on EU membership is casting doubt on the future of the country's integration with Europe, which began back in 1963.
Cyprus is the main sticking-point. Turkey's relations with Europe may suffer lasting damage unless a solution is found quickly.
In a recent opinion poll only one in three Turks said they definitely want their country to join the EU - about half the figure in similar polls two years ago.
Turkey is the only candidate ever to have been obliged to start accession talks on the basis that it may never be granted full membership, even if it passes every test.
France's bill on Armenian 'genocide' denial triggered angry protests
And last month the French parliament sought to embarrass Turkey over the nation's past history, by voting for a bill which would make it a crime to deny Turkish responsibility for "genocide" against the Armenians in World War I. That provoked a wave of angry anti-French demonstrations in Turkey.
In fact, Europe's reputation for arrogance among the Turks has united the main political currents there in protest against what they see as "unfair" treatment.
Consider these recent statements by influential Turkish figures:
- Prime Minister Recep Tayyip Erdogan has said he would rather see the suspension of the EU membership talks than bow to what he calls "unreasonable" demands over Cyprus.
- Former Turkish president and prime minister Suleyman Demirel says EU demands for legal rights for Turkey's Kurdish minority may threaten the unity of the state, which Turkey "will not accept."
- Onur Oeymen, deputy leader of the opposition Republican People's Party and a former ambassador to Nato, accuses the EU of seeking excuses to delay or block Turkish membership. He complains that Europe's present leaders lack "strategic vision", and fail to understand the importance of supporting Turkey, as the only secular democracy in the Muslim world.
- Mehmet Ali Birand, a popular TV newscaster, says Turkey has been faithful to Europe for 45 years, but Europe has not. Now he fears that Europe is going to "break the dream".
In Europe, the cooling of political attitudes towards Turkey, fuelled by public fears of immigration and suspicion towards Islam, has been dramatic.
Some opinion polls suggest that opponents of Turkish membership account for two-thirds of the population in France, Greece and Cyprus. In Austria it is around 80%.
A turning-point was last year's referendums in France and the Netherlands, when voters rejected the draft EU constitution.
After that, conservative leaders such as Angela Merkel in Germany and Nicolas Sarkozy in France spoke out loudly against full EU membership for Turkey, even in 15 or 20 years time.
Turkey's Muslim make-up has also become an issue.
Hans-Joerg Kretschmer, the EU's ambassador in Ankara, says Europe wants to see "for the first time in the history of mankind whether a Muslim country is able and willing to embrace the values of Western civilisation".
But Turkey's Foreign Minister Abdullah Gul says Turkish EU membership would prove that the EU "does not belong to a single religion".
He insists his government is fully committed to a long-term political "marriage" with Europe, and speaks proudly of Turkey's radical pro-European reforms as a "silent revolution".
The European Commission itself has praised Turkey for abolishing the death penalty, taking action against police torture and changing the constitution to rein in the influence of the army.
But now the Commission is focusing again on shortcomings in Turkish democracy. It has warned of a "train crash" unless Turkey bends to EU demands over Cyprus and moves to bolster civil rights.
"We will not do it!" was Mr Gul's terse reply, when asked whether his government would fulfil the EU's demand to end its embargo on ships from Cyprus using Turkish ports.
"The Europeans must first fulfil their promises", he said, meaning that the EU should first take steps to facilitate direct trade with the Turkish Cypriots in northern Cyprus.
In 2004 the Turkish Cypriots voted in favour of an international peace plan to unite the divided island. The Greek Cypriots, who represent the only internationally recognised government there, voted against the plan but were anyway admitted as EU members. Now they, like every member-state, hold a veto over Turkey's progress.
Trade and investment
Still, a "train crash" is not inevitable. Turkish leaders now say they may amend a much-criticised law banning insults against "Turkishness", which has been used against authors who have written critically on Kurdish and Armenian issues.
Britain, Finland and other supporters of Turkey's case argue that its progress must not be seriously held back.
It is clear that the EU itself could hardly escape without damage in case the relationship turned sour.
Turkey is now one of the most attractive partners for European trade and investment. French car-makers and Austrian banks are among those profiting from Turkey's booming economy and liberalising market.
Michael Lake, a former EU envoy to Turkey, warns that to block Turkey's EU prospects would harm the EU's credibility.
And Onur Oeymen says it would be a massive strategic mistake for the EU to write Turkey out of its future plans - because then, he said, "you are going to make Turkey your competitor, if not your enemy".