Greece's leftist-led government was expected to shrug off a censure vote and protests on Saturday as it prepares to sign a provisional deal to end a 27-year name row with Macedonia.
The vote was to take place a day before the foreign ministers of Greece and Macedonia meet on the border to hold a landmark signing ceremony.
"The agreement to resolve the longstanding dispute over the name issue with the Former Yugoslav Republic of Macedonia is a victory of historic importance for Greece," Prime Minister Alexis Tsipras said late Friday.
"We proved that where there is a will, a decades-old dispute can be resolved in a balanced way," he said.
The agreement, which will eventually see Greece's northern neighbour renamed the Republic of North Macedonia, has been welcomed by the United Nations, the European Union and NATO.
Athens had long objected to it being called Macedonia because it has its own northern province of the same name, which in ancient times was the cradle of Alexander the Great's empire -- a source of intense pride to modern-day Greeks.
But earlier this week, Tsipras and his Macedonian counterpart Zoran Zaev reached a deal to end the festering dispute.
Senior EU officials are to attend Sunday's ceremony in the Prespes Lakes district, according to Greek reports.
Officials in Athens says it will help stabilise the historically volatile Balkan region, permitting Greece to focus on other regional challenges, Turkey among them.
But from the moment the details emerged, a political storm erupted in both countries.
Greece's main opposition conservatives tabled a censure motion while Macedonia's pro-nationalist President Gjorge Ivanov has pledged to exercise a one-time veto to delay the deal.
Skopje hopes to secure a date to begin European Union accession talks at an EU summit in late June and an invitation to join NATO in mid-July.
In Athens, there is anger over the government's acceptance that its neighbour will be able to refer to its language and ethnicity as "Macedonian".
"Nobody can be called Macedonians except the Greeks," protest organiser Michalis Patsikas told state agency ANA.
But to Macedonians, who have espoused this identity since the days of Yugoslavia's Marshal Tito, the notion of revising their name and constitution is anathema.
"This is an absolute defeat of the Macedonian diplomacy in every possible way," Hristijan Mickovski, who heads the main opposition VMRO-DPMNE party, said this week.
Tempers flared in Greece's parliament on Friday, with a lawmaker from neo-Nazi Golden Dawn calling on the Greek army to topple the government.
Outside the chamber, a few hundred people, including priests and Golden Dawn lawmakers, gathered to protest.
"History is written in blood," said one banner held up by a monk, while another read: "Skopje = Monkey-donia."
The protesters plan to remain outside parliament until the censure vote, while another demonstration will be held on the border on Sunday.
Tsipras' domestic critics say he has bargained away Greece's diplomatic advantages -- the power of veto over EU and NATO accession -- for a deal that could backfire.
"There is no chance that those speaking a 'Macedonian' language will be called 'North Macedonians'," said New Democracy leader Kyriakos Mitsotakis.
"We will not divide the Greeks in order to unite the (Macedonians)," he said.
Opposition is even stronger is Greece's north, where Greek and Bulgarian guerrillas fought a bloody war in the early 20th century for control of then Ottoman-held Macedonia.
In a paradox, Tsipras' nationalist coalition partner, the Independent Greeks party, are expected to support the government on Saturday but reject the Macedonia deal whenever it goes to a vote.
The agreement still needs to be approved by Macedonia's parliament and pass a referendum there as well as being ratified by the Greek parliament, a process likely to take months.