The bone of contention, yet again, is the divided island of Cyprus, with whose internationally recognised Greek-Cypriot government the European Union will open entry negotiations next year - to the delight of Athens but the undisguised fury of Ankara, whose own application for membership the EU has again put on hold.
After talks here with Tony Blair, the Greek Prime Minister, Costas Simitis, was adamant: unless Turkey played by the rules of the European club and dropped its threats to incorporate the Turkish-Cypriot third of the island, "Greece is prepared to prevent Turkey taking part" in the unprecedented gathering of current and aspiring EU member countries.
But just a mile away from the Greek embassy residence where Mr Simitis was speaking to journalists, a top Turkish diplomat declared that Ankara would leave no stone unturned to have the entry negotiations with Cyprus declared illegal because they were in breach of existing treaties.
Inal Batu, in charge of Cyprus affairs at the Turkish foreign ministry, told a conference on Cyprus that Brussels should put the accession negotiations with the island on hold until both Turkish and Greek Cypriot communities were represented in its government.
For Britain, which aims to make the kick-off of enlargement talks the centrepiece of its EU presidency in 1998, Greece's stance is a major worry. Technically, Britain can invite whoever it likes to the conference, which will open in Buckingham Palace. In practice though, a deal will have to be worked out at the forthcoming EU summit in Luxembourg, which is expected to endorse the European Commission's recommendation that entry negotiations begin with Poland, Hungary, the Czech republic, Slovenia, Estonia and Cyprus - but not the eternally jilted suitor Turkey.
Greece apart, most if not all EU countries are happy to have Ankara there. But the conditions set out by Mr Simitis yesterday seem to leave scant room for manoeuvre. "This is not an idle threat," a Foreign Office official admitted last night, "but we have to hope it can be overcome."
Upping Athens' earlier demands, the Greek prime minister said not only must Turkey drop its attempts to prevent the negotiations with Cyprus, but it must improve its humans rights record and accept the jurisdiction of the International Court in the Hague - which Greece believes favours its position in the separate dispute with Ankara over territorial waters.Reuse content