Greece and Macedonia set aside three decades of dispute on Sunday as they agreed on a new name for the former Yugoslav republic, paving the way for its possible admission to the European Union and North Atlantic Treaty Organisation.
"We are here to heal the wounds of time, to open a path for peace, fraternization and growth for our countries, the Balkans and Europe", he said, adding that the time had come again "to sing happy songs in the Balkans".
"We have a historic responsibility that this deal is not held in abeyance, and I am confident that we will manage it", Greek Prime Minister Alexis Tsipras said as he and his Macedonian counterpart Zoran Zaev received a standing ovation from guests at the lakeside ceremony.
Mr Tsipras and Mr Zaev will also be present.
And in Psarades, priests rang the local church bell in a sign of mourning, an AFP reporter said.
The Prime Ministers of Greece and FYROM, Alexis Tsipras and Zoran Zaev, are scheduled to meet in a spot on Prespes Lake, a body of water in northern Greece that borders both countries and has been chosen for its symbolism. Zaev has said he will put the deal to a referendum in the fall.
Many Greeks are opposed to Skopje's use of the name Macedonia, as they say, it appropriates Greek history and fails to distinguish itself from the Greek region with the same name.
The agreement was signed on June 17 by the nations' foreign ministers at Lake Prespa along the border separating the Balkan neighbors.
Athens refused to accept it, saying it implied territorial claims over the Greek province of Macedonia and an appropriation of ancient Greek culture and civilisation.
United Nations mediator Matthew Nimetz congratulated the two leaders, adding that the agreement was an honorable deal.
Thousands of Greeks protested outside Parliament against the accord with Macedonia, waving Greek flags and chanting anti-government slogans, calling for Mr Tsipras to resign.
The two premiers, born just months apart in 1974, have bucked strong hostile reactions at home to push ahead with the agreement. That approval is far from assured, as it faces stiff opposition from the Greek public, and Macedonia's president has vowed to block the deal.
Tsipras has been accused of treachery by Greek hardliners, and on Saturday defeated a vote of censure against his government amid protests and clashes with police outside parliament.
In Macedonia, the agreement must clear the hurdles of parliamentary ratification, a referendum in September and a constitutional amendment.
Greece and Macedonia are about to sign a deal that, if ratified, will resolve a decades-old dispute concerning Macedonia's name.
A flare thrown by protesters highlights riot police guarding the parliament during a demonstration against the agreement between Greece and Macedonia over a dispute of the former Yugoslav\'s republic name, in Athens, on Saturday. "It knows that this will see Macedonia join North Atlantic Treaty Organisation", said James Ker-Lindsay, professor of politics and policy at St. Mary's University in London.