A United Nations mediator is visiting Athens amid redoubled efforts to end a quarter-century dispute between Greece and neighboring Macedonia over Macedonia's name.

Matthew Nimetz will meet Greek Foreign Minister Nikos Kotzias Tuesday, and will later travel to Skopje for talks with Macedonian officials.

The dispute broke out after Macedonia, for decades a part of the former Yugoslavia, gained independence in 1991. Greece objects to its use of the name Macedonia, arguing that this implies territorial claims on its own adjoining province, also called Macedonia.

Officials in Skopje counter that their part of the world has been known as Macedonia for a long time.

The squabble has prevented Macedonia from joining NATO, to which Greece already belongs. The two countries' governments have pledged to seek a solution this year.