Macedonia and Greece have been at loggerheads since Skopje declared independence from then-federal Yugoslavia in 1991, but the case escalated when Macedonia filed a lawsuit with the International Court of Justice in November 2008.

The suit called on the court to order Greece to meet its international obligations under a 1995 treaty and allow Macedonian accession to the trans-Atlantic military alliance.

Macedonia had hoped to be invited in 2008 to join NATO, but Greece barred the way because of a dispute over Macedonia’s name, which is also the name of Greece’s northern province.

In a case that will determine whether Greece has the right to block the NATO bid, both states will present their arguments to the 15-judge panel over six days of hearings this week and next, following the filing of undisclosed written submissions.

Lawyer Philippe Sands, speaking for Macedonia, told the Hague-based court that Macedonia’s name never had been intended to portray “any territorial claim” to Greek territory, neither at the time of its independence or now.

He said the case was instead about a “blatant violation” of an international treaty and a “matter of respect for a treaty.”

Macedonia says Greece violated a 1995 accord signed by the two countries in which Skopje agreed to use a provisional name, “The Former Yugoslav Republic of Macedonia,” in international organizations and that Greece had agreed not to block Macedonia’s integration into the European Union and NATO.

Greece objects to the name Macedonia, saying it implies a claim to its northern province and has argued the ICJ has no jurisdiction to hear the case.

United Nations talks have failed to resolve the deadlock.

Citing a matter of “tremendous importance” to Macedonia’s multi-ethnic democracy, Foreign Minister Antonio Miloshoski said Skopje had been left no choice but to start legal proceedings, but would remain committed to mediation over its name.

Macedonia was recognized by the UN in 1993 under the name Former Yugoslav Republic of Macedonia. But more than 100 states, including four permanent members of the UN Security Council, have recognized the Balkan state as the Republic of Macedonia.