NATO leaders are ready to welcome in three new Balkans members this week but a Greek veto could torpedo Macedonia's entry, while allies remain divided over two hopefuls on Russia's southern flank.
At NATO's summit, in Bucharest starting Wednesday, the world's biggest military alliance is set to endorse the technical preparations undertaken by Albania, Croatia and Macedonia to enter the fold.
But as NATO gears up its operations for the 21st century, an extremely old political argument about the name "Macedonia", with its links to Alexander the Great, could stop the tiny state from joining.
Ahead of the meeting, to be attended by some 60 heads of state and government, host President Traian Basescu said that handing invitations to the three Balkans hopefuls would "guarantee the summit's success".
He also urged NATO to invite Georgia and Ukraine to join its membership action plan (MAP), designed to prepare countries for entry, even though Russian President Vladimir Putin is likely to raise new objections at the summit.
"We must give these two countries the chance to accomplish their wish of becoming NATO members as soon as they have fulfilled accession criteria," Basescu said.
However the allies are split over such a move, with opponents including Germany, France, Italy and Spain suggesting it could destabilise the region.
Ahead of the summit, Albania, Croatia and Macedonia have lobbied frantically, with US backing, and their efforts have been widely praised.
"Very few people are talking of anything other than three" being invited in, said one senior NATO diplomat.
But Greece refuses to recognise the former Yugoslav republic's name because it is the same as that of the northern Greek province of Macedonia and Athens worries that this could imply a claim on its territory.
Macedonia's constitutional name is "Republic of Macedonia", and Skopje wants this used in international relations, except with Athens, where a name acceptable to both parties would be found.
"Greece thinks nothing will be ready within a week to find a solution," a European diplomat warned Saturday, after talks involving Greek Foreign Minister Dora Bakoyannis.
Georgia and Ukraine's hopes of being invited into the MAP programme face far more hurdles, with officials and diplomats suggesting that up to 12 nations are opposed.
Many have expressed deep concern about the state of emergency Georgia imposed in December to end opposition protests, as well as its frozen conflicts with separatist Abkhazia and South Ossetia.
Russia's ambassador to NATO, Dimitry Rogozin, said this month that membership for Georgia would incite both northern regions to break away and that this would destabilise Russia.
Meanwhile Ukraine's leaders are keen to move ahead, but there is wide public opposition and NATO is concerned that efforts might be blocked by the parliament in Kiev.
"A country should become a NATO member not only when its temporary political leadership is in favour but when a significant percentage of the population supports membership," German Chancellor Angela Merkel said this month.
She added: "Countries that are themselves entangled in regional conflicts, can in my opinion not become members."
Georgian Foreign Minister David Bakradze has urged NATO countries not to cave in to Russian pressure and warned that a "policy of appeasement" could only bring limited, short-term gains.
One thing is certain, NATO insists that Moscow can have no veto.
"The history of the enlargement process is that it has clearly demonstrated that it contributes to security and stability throughout Europe, and in no case has had the opposite effect," chief spokesman James Appathurai said.
"European democracies have the right to apply for NATO membership and NATO's door is open to them when they meet NATO standards," he said. "That process is not open to influence from outside parties."