SOUNION, Greece (Reuters) - The foreign ministers of Greece and Macedonia held “hardworking and intense” talks on Saturday to bridge their differences in a decades-old dispute over the name of the former Yugoslav Republic that has complicated its hopes of joining the EU and NATO.

The row began in earnest in 1991, when Macedonia broke away peacefully from former Yugoslavia, declaring its independence under the name Republic of Macedonia.

Greece, which has its own region called Macedonia, has asked its neighbour to change its name, as well as what it says are “irredentist” references denoting territorial ambitions in Skopje’s national constitution, which Greece says must be taken out.

“I can characterise the meeting as being very serious, hardworking, intense a few times,” said Matthew Nimetz, an American diplomat who has been the United Nations special envoy on the name dispute since 1994. He was speaking after the conclusion of a meeting of the two foreign ministers at a resort east of Athens.

Positive work had been done, he said, and the two ministers would be briefing their prime ministers who were expected to meet in Bulgaria on May 17 on the sidelines of an EU-Western Balkans summit.

The two countries decided last year to renew their efforts to try to reach a settlement well before the summer.

The foreign ministers, Nikos Kotzias of Greece and Nikola Dimitrov of Macedonia, did not take questions. In statements on Friday, Dimitrov said discussions were at a pivotal point.

“We are in a very delicate phase ... in a way tackling one of the last remaining differences,” Dimitrov said.

Both sides see 2018 as a year of opportunity.

Greek Prime Minister Alexis Tsipras hopes to resolve the matter to gain more political leverage in Europe, and at the same time increase his popularity at home where many Greeks feel the country’s debt crisis and three massive bailouts have compromised its sovereignty.

Meanwhile, Macedonia’s Prime Minister Zoran Zaev, who came to power a year ago, wants to accelerate his country’s accession to NATO and the EU to boost international support for his fragile coalition.

Greece has said a compromise could include a compound name with a geographical or chronological qualifier by which the country would be known and referred to in all international institutions - the so-called “erga omnes”.

Examples could include Upper Macedonia and North Macedonia.

Pending a settlement, the ex-Yugoslav nation was admitted to the United Nations in 1993 under the name Former Yugoslav Republic of Macedonia (FYROM).