Macedonia's president said that he would not sign off on a historic deal that would change the country's name, the most potentially disruptive reaction so far to the agreement with Greece that has received diverging reactions in both countries.

President Gjorge Ivanov said the agreement, which would rename Macedonia as the Republic of North Macedonia, gave too many concessions to Greece.

"Such a harmful agreement, which is unique in the history of mankind, is shameful and unacceptable for me," Ivanov said in a TV address. "It violates the Constitution [and] the laws ... I will not legalize political illegal agreements."

The deal reached by the prime ministers of the two countries is expected to be signed by their foreign ministers this weekend. After that, Macedonia's parliament would vote on it, and if it is approved, Ivanov's signature would be needed. If the president refuses to sign, the deal would return to parliament for another vote. Ivanov would have to sign off on the agreement if it is passed a second time.

The name dispute, which has prevented Macedonia from joining international institutions such as NATO, has roused strong nationalist sentiments and poisoned the two countries' relations since the Balkan country declared independence from Yugoslavia in 1991.

Greece argues that the term "Macedonia" implies a claim on the territory and ancient heritage of its own northern province of the same name — the birthplace of ancient warrior king Alexander the Great.

The agreement reached by Prime Minister Alexis Tsipras and Macedonian Prime Minister Zoran Zaev has strong dissenters, with opponents staging large protests on both sides of the border. The issue threatened to split Greece's governing coalition, and provoked a rift between Zaev and his president.