Turkey used to be a dreaded invader of Europe, but these days it is more like a patient suitor. For 43 years, since signing an association agreement, Turkey has been waiting to become a full-fledged member of the Europe Union. But each time the desired goal has seemed to be within reach, a new obstacle has sprung up along the way.

Meanwhile, numerous other countries have moved ahead to join the European Union with great fanfare. In fact, the European Union (and its previous incarnation, the European Economic Community) has grown from six to 25 members and now encompasses most of Western Europe, Scandinavia, Central and Eastern Europe. Even the Balkans is inching toward inclusion in the EU. Yet, leaving Turkey behind would be a mistake of monumental proportions.

There is no doubt Europeans are decidedly reluctant to let Turkey into their club. When asked, Europeans will tell you that Turkey is not politically or economically ready for EU membership. Underlying these factors, however, are centuries of history, culture, ethnicity and religion, as well as the existential question -- "what is Europe?" -- which Europeans are finding hard to answer. (The French and Dutch rejections of the European Constitution have not made this any easier.) Whatever Europe is, though, most Europeans clearly feel today that Muslims are not Europeans.

On Monday, it almost happened again. Long-awaited Turkish EU membership talks that had been set for Oct. 3 were stalled by the government of Austria, which raised last-minute objections and suggested that the EU should consider the option of "privileged partnership" for Turkey. Turkish Prime Minister Recep Tayyip Erdogan rejected the idea out of hand, and again deadlock threatened.

Why Austria? Perhaps because the Austrians and the Turks have centuries of violent history between them, going back to 1683 when a great Roman Catholic Army fought the Ottoman Turks back at the gates of Vienna and halted Turkish advance.

Many today wonder if the Turks are back to finish the job of Muslim expansion into Europe, fearing a "clash of civilizations." A recent poll by the German Marshall Fund recorded that Europeans are deeply divided and confused about Turkish membership with as many as 40 percent continent wide being in doubt. In Germany, Angela Merkel, leader of the Christian Democrats and the country's most likely next chancellor, has come out categorically against Turkish membership. Former Dutch European commissioner Frits Bolkestein a few weeks back warned of the Islamisation of Europe, and said that if Turkey becomes an EU member "The relief of Vienna in 1683 will have been in vain." History casts a long shadow on the European continent.

But if the past is prologue, it does not have to be destiny. Turkey is geographically as well as historically at a crossroads, having spent the 20th century in a drive toward modernity and secularization started by Mustafa Kemal Ataturk, the founder of the modern Turkish state. Mr. Erdogan's government itself has demonstrated great determination to adopt the reforms demanded by the EU as criteria for membership, including minority rights for Turkey's Kurdish minority, abolition of the death penalty, military reforms aimed at reducing its influence on governance. The drive toward the EU is itself transforming Turkish society.

At the meeting between the Muslim and Christian worlds, Turkey has a pivotal role to play, and it is very much to the long-term advantage of Europe and the United States to anchor this populous, Western-oriented, Muslim country in our economic and political systems. As a NATO ally, Turkey remains strategically vital, though it is obviously not to be taken for granted as the Bush administration found in the run-up to the Iraq War. A Turkey cut adrift, disaffected by the rejection of Europeans, and bordering the Middle East and the unstable Causacus region, is not a happy prospect.

Will there be more roadblocks for Turkey in the future? It is entirely possible, as there is the possibility that Turkey might not join in any of our lifetimes. Even as President of the European Commission Jose Manuel Barroso welcomed the opening of talks on Monday, stating that "A stable, modern and democratic Turkey is an objective we should support actively in the European Union and in Turkey," he also added, "Of course the road towards Turkey's accession will be long and difficult. Accession, as for every country, is neither guaranteed nor automatic." Only the most ardent suitor would find words like these to be an encouragement.

Helle Dale is director of the Douglas and Sarah Allison Center for Foreign Policy Studies at the Heritage Foundation.