Greece on Tuesday said there was still "some distance" left to go to resolve a quarter-century name row with neighbouring Macedonia, as the two countries' leaders prepare to meet this week.
Expectations of a deal rose this week as a meeting in Sofia was announced between Greek Prime Minister Alexis Tsipras and his Macedonia counterpart Zoran Zaev on Thursday.
But Greek government spokesman Dimitris Tzanakopoulos insisted Tuesday that "another round may be needed to cover the distance separating the two sides".
"There is still some distance (to cover)," Tzanakopoulos told reporters.
In Skopje, Prime Minister Zaev told reporters that he expected "dates for the starting of formal negotiations" on the issue.
Macedonia hopes that to be in June, he said.
"We would like to find the final solution, but not at any price," Zaev said.
Officials had previously said that the two leaders would only meet if there was a chance of an accord.
The long-running name dispute between Macedonia and Greece dates back to 1991, when Skopje declared independence following the collapse of communist Yugoslavia.
Athens objects to Macedonia's name because it has its own northern province called Macedonia, and fears it may imply territorial ambitions.
The spat has hampered Macedonia's ambitions to join the European Union and the NATO military alliance.
"Thursday's meeting between the prime minister and his counterpart Mr Zaev will be particularly useful and important, but we cannot anticipate an accord," Tzanakopoulos said.
A Macedonia government source on Tuesday confirmed that the main remaining difficulty is over the official name of the landlocked Balkan country's language.
Greece wants any changes to be enshrined in a revised Macedonian constitution, which Zaev's government currently lacks the parliamentary majority to enforce.
Tzanakopoulos on Tuesday left open the possibility of an international treaty setting out a binding roadmap for future constitutional revision.
When the two leaders last met in Davos, Switzerland in January, Zaev made a gesture of conciliation in renaming Alexander the Great airport in Skopje, a name that had long riled the Greeks.
The motorway linking Macedonia with Greece was also renamed the Friendship Highway.
Because of the dispute, Macedonia was forced to join the United Nations under the name the Former Yugoslav Republic of Macedonia (FYROM).
Among possible new names, Gorna Makedonija or Upper Macedonia is the most frequently mentioned.
Macedonia decided to change the name of the "Alexander of Macedonia" highway in February 2018 as part of its efforts to resolve a name row with Greece