Greek Prime Minister Kyriakos Mitsotakis aired his misgivings in Washington on Tuesday over recent flagrant violations of the landmark Prespa Agreement by the new leadership of the Republic of North Macedonia, warning that the specific international treaty is non-negotiable.

Mitsotakis appeared at a discussion at the D.C.-based Council on Foreign Relations alongside former US ambassador to Greece Daniel Speckhard (2007-2010), the CEO and president of the non-profit Corus International organization.

The Greek leader is in the US capital to attend a NATO summit.

Among others, Mitsotakis said one problem in the Balkans is the resurgent specter of nationalism “when nobody necessarily expects it.”

“Today, North Macedonia is a member of NATO because Greece withdrew its veto following the Prespa Agreement that was signed and ratified by the previous government. We have clarified that it is an international treaty that places the country under obligations. We respected it and we respect it.

“One of the fundamental – if not the  most fundamental – doctrines, aspects of this agreement relates to the name ‘North Macedonia’, that is used erga omnes (in all uses). And this is something that is very clear and non-negotiable for Greece. When I hear that the new government refers to the country as Republic of Macedonia, domestically, I have serious concerns. And this is an issue I plan to raise. It is not constructive and it does not help North Macedonia’s European path,” Mitsotakis emphasized.