SKOPJE, March 13 (Xinhua) -- The United States supported the efforts carried out by the Macedonian and Greek authorities in solving their name dispute issue, US Assistant Secretary of State for European Affairs, Wess Mitchell, said on Tuesday at a press conference with Macedonian Prime Minister Zoran Zaev.

Asked whether the U.S. would become part of the negotiations, Mitchell said that both countries were the ones to reach the solution to the long-standing issue existing between them.

"The only durable solution will be a joint solution. Macedonia has taken tremendous steps forward to engage in the negotiations with its Greek interlocutors and there is tremendous opportunity, greater than we have ever had," Mitchell told reporters here.

Talking about Macedonia's aspirations to join NATO, the U.S. official said that NATO's doors remained open and that the U.S. backed the country's drive towards NATO accession.

"There are some milestones coming up in terms of how we can mark the progress. U.S. commitment to Macedonia is to finding a solution that paves the way to NATO and the EU. It has been our commitment for some time and it will continue to be our commitment and is not tied to a date or an event," Mitchell told reporters.

Meanwhile, Prime Minister Zoran Zaev said at the joint conference Macedonia and Greece had already started the final phase of the talks concerning the solution of the name dispute.

Zaev also said that every help coming from strategic partners such as the U.S., would be welcome while he highly praised the mediation performed by the United Nations mediator Mathew Nimetz.

"The name issue solving process is brokered by the UN. Mediator Matthew Nimetz is one of the most proficient in the essence of the problem," Zaev said.

Zaev also said he expected Macedonia in April to receive a clean recommendation for the opening of negotiations with the EU, followed by their launch in June, and Macedonia at the July Summit to become the 30th member of NATO.

Athens and Skopje have been at odds over the use of the name of Macedonia since Greece's northern neighbor broke away from Yugoslavia in 1991.

Macedonia is formally called Former Yugoslav Republic of Macedonia (FYROM) at the UN. Macedonia is also the name of a northern province in Greece and Athens is worried that the use of the same name by the neighboring state could lead to territorial claims.

The solving of name row that exists between the two countries is seen as the main obstacle that Macedonia has to overcome in order to make progress towards the European Union and NATO integration.