ATHENS (Reuters) - Greek Prime Minister Alexis Tsipras failed to get backing from the main opposition leader on Saturday to build consensus ahead of intensified talks between Greece and Macedonia on resolving a decades-old name row.

FILE PHOTO - Greece's Prime Ministers Alexis Tsipras gestures as he speaks during the World Economic Forum (WEF) annual meeting in Davos, Switzerland January 24, 2018. REUTERS/Denis Balibouse

Athens and Skopje have agreed to step up negotiations to reach an accord in a dispute which has stymied the ambitions of the tiny but strategically-placed ex-Yugoslav republic in joining NATO and the European Union.

Greece believes the name Macedonia implies a territorial claim over its own northern region of that name. Hundreds of thousands of Greeks rallied in the northern city of Thessaloniki earlier this month to protest against the use of the name “Macedonia” in any solution to the row.

There have been some suggestions there could be a two-name solution such as Northern Macedonia or Macedonia-Skopje.

“We will not divide Greeks to unite Skopje,” Conservative New Democracy party leader Kyriakos Mitsotakis said in a televised address after a meeting with Tsipras.

He said resolving the name dispute was not just a foreign policy matter but a serious issue relating to Greece’s history and “the very identity of Greeks”.

As a member of both, Greece’s assent is needed for its neighbor to join NATO and the EU, but the name “Macedonia” is perceived to denote irredentist ambitions against its own northern province of Macedonia.

It is an issue that sometimes mystifies foreigners, but which is deeply felt among many Greeks.

Mitsotakis, whose party is leading in opinion polls, blamed Tsipras for not asking for constitutional changes in Skopje as a “necessary precondition” for any talks, noting that the window of opportunity for a deal has closed.

A United Nations envoy, Matthew Nimetz, is due in both countries next week to further discussions.

WANTED: MUTUALLY ACCEPTABLE SOLUTION

In a televised address after meeting leaders of all political opposition parties, Tsipras vowed to press on with efforts to find a “mutually acceptable” solution, saying failure to do so would not benefit Greece or stability in the Balkans.

He said the new political leadership in Skopje had withdrawn some of the irredentist rhetoric of past governments, a catalyst to intensify talks.

“The most crucial point that must become clear is that solving our differences with FYROM is not an obligation toward third parties but serves our medium-term national interests and of course stability in the Balkans,” Tsipras said.

Talks between the two states have been inconclusive since 1991, when Macedonia withdrew from former Yugoslavia. It was admitted into the United Nations in 1993 under the name Former Yugoslav Republic of Macedonia, sometimes referred to as FYROM.

Talks are taking place against a backdrop of mounting public sentiment in Greece against any deal which could include the name Macedonia. The large turnout at the Thessaloniki rally on Jan. 21 was unexpected, and another demonstration is scheduled in Athens on Feb. 4.

Tsipras accused the conservative opposition of a “hypocritical” stance on the issue in taking advantage of the sensitivities of Greeks. He said now was not the time for nationalist fervor or cries of fanaticism.

On Friday, Greece’s influential Orthodox Church entered the fray, saying it was against any accord with the neighboring country including the name Macedonia.