Macedonia signed accession papers with NATO on Wednesday, February 6, a key step on the way to joining the alliance after resolving a long-running name row with Greece.

The Macedonian Foreign Minister Nikola Dimitrov and representatives of all current NATO members signed the protocol at alliance headquarters in Brussels.

NATO Secretary General Jens Stoltenberg said it was a “historic day” which will lead to Macedonia becoming the 30th alliance member once the deal has been ratified by all the other capitals.

“All #NATO Allies have signed the Accession Protocol with Macedonia, which will bring more security & prosperity to the whole region. I look forward to the day when 30 flags will fly outside NATO HQ,” Stoltenberg tweeted.

Today is a historic day. All #NATO Allies have signed the Accession Protocol with ????????, which will bring more security & prosperity to the whole region. I look forward to the day when 30 flags will fly outside NATO HQ. pic.twitter.com/trPtvsn3MD — Jens Stoltenberg (@jensstoltenberg) February 6, 2019

The agreement last month with Greece to change the name of the former Yugoslav republic to the Republic of North Macedonia ended one of the world’s longest diplomatic disputes and paved the way for Skopje to join NATO and the European Union.

The E.U.’s enlargement commissioner Johannes Hahn also tweeted congratulations, saying the move was “a contribution to peace and stability” in the Western Balkans.

With reporting from AFP