They're Europe's odd couple--Turkey's Prime Minister Recep Tayyip Erdogan, a devout Muslim with a background in political Islam, and his Greek counterpart Kostas Karamanlis, an Orthodox Christian from Greece's traditionally anti-Turkish right. Yet despite their countries' age-old enmity, the pair have forged a surprising political and personal friendship. In July, Karamanlis was the chief witness at the lavish Istanbul wedding of Erdogan's daughter, Esra. This month Erdogan attended the opening of the Olympic Games in Athens as Karamanlis's honored guest, and there are rumors that Karamanlis will be making a return visit in September to stay at Erdogan's Black Sea summer house. "They joke around like Gorby and Reagan," says a Western diplomat who has witnessed the chemistry at first hand.

Could they produce a similar thawing in one of Europe's historically frostiest relationships? For Erdogan, hoping to start accession talks with the European Union in December, the stakes in befriending the Greeks couldn't be higher. Though Ankara has its differences with Turko-skeptics like France and Austria, it's the Greeks and Greek Cypriots who have the strongest traditional enmity toward their old colonizers. As recently as the late 1990s, Athens and Ankara almost went to war over airspace and naval rights in the Aegean. Karamanlis thinks burying the hatchet with Turkey will bring economic benefits to the whole Eastern Mediterranean. "A European Turkey is in everyone's best interests," he says.

The fresh thinking reflects the two men's politics. Erdogan and Karamanlis are both center rightists, they're young (Karamanlis is 47, Erdogan, 50) and both have effected political revolutions. Karamanlis overturned the 23-year dominance of Greece's socialists in a surprise election victory in March; Erdogan overcame widespread suspicion of his Islamist-based party to sweep away Turkey's old political class in 2001. They share a vision of a united Europe that supercedes the prejudices of the older generation.

That meeting of minds has already translated into concrete actions. In April, when Greek and Turkish Cypriots voted in a referendum on reunification, Karamanlis tried to persuade the Greek Cypriots to vote yes. He failed--but his efforts were telling. In Brussels, the Greeks have been among the staunchest supporters of Turkey's EU bid. This good will could be further tested in coming months. Speculation is rife that the two men may try to translate their friendship into an amicable resolution of long-running disputes about territorial waters and airspace in the Aegean. Meanwhile, back in April the EU promised Turkish Cyprus a partial lifting of an economic embargo if it voted to reunify with its Greek neighbors. The Turkish Cypriots fulfilled their part of the bargain--but now Greek Cyprus, a full-fledged member of the EU since May, has threatened to block a 259 million euro aid package and the reopening of direct flights to airports in the north. Athens could be the key to persuading its Cypriot cousins to drop their veto plans.

That puts Karamanlis in a tricky position, because his pro-Turkish stance isn't shared by many in Greece. Will he risk strife at home to protect the interests of his new buddy Erdogan? That'll be the true test of their friendship.