A dispute over the name of Macedonia could derail Nato plans to invite three Balkan states to join the alliance.
Greece has said it cannot support Macedonia's bid to join Nato, because of an unresolved dispute over its Balkan neighbour's name.
Nato foreign ministers have begun discussing whether Albania, Croatia and the former Yugoslav republic should be asked to become members next month.
Greek Foreign Minister Dora Bakoyannis told reporters in Brussels that Athens backed inviting Albania and Croatia but could not consent to asking Macedonia.
All 26 members of the alliance have to agree, but Greece has threatened to block Macedonia's bid because of the northern Greek region of the same name.
The decision threatens to derail Nato's plans to invite all three Balkan states at a summit in Bucharest in April.
A UN envoy is currently trying to find a compromise for both countries.
Athens objects to its neighbour taking the name of a northern Greek region.
It says the name implies a territorial claim on the region, which Macedonia denies.
A lot depends on the question of whether these two states are going to be able to come closer together in the coming weeks Frank-Walter SteinmeierGerman Foreign Minister
A lot depends on the question of whether these two states are going to be able to come closer together in the coming weeks Frank-Walter SteinmeierGerman Foreign Minister
Greece says the name implies a territorial claim on the region, which Macedonia denies.
Ms Bakoyannis made the comments in a speech handed to reporters after a meeting of Nato foreign ministers.
"Unfortunately the policy followed by the government of the Former Yugoslav Republic of Macedonia in its relations with Greece, particularly as concerns its intransigent stance and its actions of an irredentist and nationalist logic, do not allow Greece to take the same positive stance as in the case of Croatia and Albania," she said.
However, she said she hoped there was still time to reach "a mutually acceptable" solution in time for next month's Nato summit.
A UN envoy is currently trying to find a compromise for both countries.
Balkan stability
Nato members are keen to extend the alliance into the Balkans, to stabilise the region after Kosovo's 17 February declaration of independence.
Nato members are keen to extend the alliance into the Balkans, to stabilise the region after Kosovo's 17 February declaration of independence.
All three countries are backed by Washington and Nato Secretary General Jaap de Hoop Scheffer said they had worked hard on political and military reforms.
All three countries are backed by Washington and Nato Secretary General Jaap de Hoop Scheffer said they had worked hard on political and military reforms.
In the long run, he said, the only recipe for Balkan stability was their integration in Nato and the EU.
In the long run, he said, the only recipe for Balkan stability was their integration in Nato and the EU.
"I would like all three countries to join," German Foreign Minister Frank-Walter Steinmeier told reporters.
"I would like all three countries to join," German Foreign Minister Frank-Walter Steinmeier told reporters.
"A lot depends on the question of whether these two states are going to be able to come closer together in the coming weeks."
"A lot depends on the question of whether these two states are going to be able to come closer together in the coming weeks."
An invitation would be made at a Nato summit in Bucharest in April.
The BBC's correspondent at the meeting in Brussels, Oana Lungescu, said unless Macedonia agreed to change its name by early April, Greece might veto its membership and cast an embarrassing shadow over its biggest ever summit.
Russian dilemma
Russian dilemma
Nato is also expected to offer closer ties to Serbia, despite the anti-Western backlash there over Kosovo.
Requests by Ukraine and Georgia to get a road map for eventual membership are also proving divisive.
Requests by Ukraine and Georgia to get a road map for eventual membership are also proving divisive.
Our correspondent says that while former communist countries support them, other Nato members are looking for ways to send a positive signal to the two former Soviet republics without worsening relations with Russia, which are at their lowest point since the Cold War.
Although Nato members want to send a positive signal to the two former Soviet republics, some do not want to risk worsening relations with Russia, which are at their lowest point since the Cold War.
Afghanistan is also on the agenda of the talks in Brussels, but a Nato spokesman said no decisions were expected on committing more troops to what is already the alliance's biggest and most challenging mission.
"In Russia we have a new president and I think the European Union wants to put its ties with Russia on another footing", Luxembourg's foreign minister Jean Asselborn said.
Foreign ministers will work instead on a strategic statement explaining why Afghanistan is key to the fight against global terrorism, and how Nato plans to improve co-ordination with other international organisations to build up the country.
"We have to take the interests of others, not only the members of Nato, into account."
Do you live in any of the three countries seeking Nato membership? What's your reaction to the talks? Send us your comments by filling out the form below.
Do you live in any of the three countries seeking Nato membership? What's your reaction to the talks? Send us your comments by filling out the form below.
