Northern Macedonia formally joined the North Atlantic Treaty Organization (NATO) and became the 30th member of it, after a long dispute with Greece over the name of the country was resolved, after the European Union agreed to start negotiations to join North Macedonia and Albania in the bloc.

"Northern Macedonia has now become a member of the NATO family, a family of thirty countries and about a billion people, a family that is confident that we are stronger and safer together, whatever challenges we face," NATO Secretary-General Jens Stoltenberg said in a statement.

Stoltenberg will chair a celebration at the NATO headquarters in Brussels next Monday, during which he will raise the flag of Northern Macedonia next to the other 29 flags.

The US State Department said the Republic in the Balkans had submitted a "accession document" to NATO, supplementing the final step in the membership path.

The move comes at the end of a successful diplomatic week for Northern Macedonia, as the European Union governments also - after several delays - agreed to start the country's accession talks to the union.

"The accession of Northern Macedonia to NATO today is the culmination of years of efforts by the government of Northern Macedonia and its people to join NATO," said US Secretary of State Mike Pompeo.

"The membership of North Macedonia in NATO will promote integration, democratic reform, trade, security and stability in the region," he added.

NATO members signed the accession protocol for Northern Macedonia in February 2019, after all the parliaments of the 29 countries ratified the membership, the last of which was the Spanish parliament.

And a NATO official said - earlier - that Northern Macedonia will not become a full member until after the signing of the protocol by the parliaments of all member states.

NATO flag in front of the Macedonian Parliament Building (Reuters)

open road
The way to join NATO and the European Union was opened to Northern Macedonia after it reached an agreement with Greece in January 2019 to change its name to the Northern Republic of Macedonia, ending one of the world's longest diplomatic disputes.

The European Union agreed on Tuesday during a video ministerial conference to start negotiations to join the bloc in Northern Macedonia and Albania.

"I am very pleased that today European Union member states reached a political agreement to start accession negotiations with both Albania and Northern Macedonia," he said in a tweet on Twitter, European Union Enlargement Commissioner Oliver Farhli said at the end of the meeting.