North Macedonia joined NATO with its constitutional name (the Republic of North Macedonia) and is represented in the Alliance with this name, a NATO official was quoted as saying on Tuesday in Brussels.

Asked about Sunday’s intentional omission of the word “North” by the landlocked southern Balkan country’s new president, Gordana Siljanovska-Davkova, during her swearing-in ceremony, the official said:

“North Macedonia is a valuable NATO ally and contributes significantly to our collective security, this includes troops deployed to our KFOR mission in Kosovo, an advisory and capacity-building mission in Iraq and NATO’s multinational battlegroups in Latvia, Bulgaria and Romania.

The Prespa Agreement paved the way for North Macedonia to join NATO and contributed to good neighborly relations, which are important to maintain between the Allies. North Macedonia joined the Alliance under its constitutional name and is represented in NATO under that name,” the NATO official was quoted as saying.

Use of the constitutional name by the country’s government, all state services, agencies and stakeholders is at the centerpiece of the 2018 Prespa Agreement between Athens and Skopje.

The 71-year-old Siljanovska-Davkova, a member of the rightwing and nationalist VMRO party, and is the country’s first female president.

The development on Sunday generated a swift and stern reaction from Greek Prime Minister Kyriakos Mitsotakis via social media, as he warned the neighboring country’s president that Greece “will not tolerate similar slips” in the future.

Additionally, the Greek Ministry of Foreign Affairs issued a statement saying that the use of the name “Macedonia” blatantly violates the Prespa Agreement, as well as the constitution of North Macedonia, and emphasized that this violation endangers the EU-candidate country’s accession to Europe.

The text of the official statement, found on ministry website, reads as follows:

“During today’s swearing-in ceremony in Parliament, and in spite of the fact that the official text of the oath that was read out to her referred to the country as ‘North Macedonia,’ the new President of the Republic of North Macedonia, Gordana Siljanovska-Davkova, chose to call her country ‘Macedonia.’