Stergios Kalogiros, a senior organizer of the Feb. 4 rally, told The Associated Press that he was optimistic that the Athens event would draw huge crowds after it won endorsements this week from powerful religious and local government organizations.
"To get attendance to reach seven figures is achievable," he said.
"Local government associations are backing the rally and say they will help mayors around the country bus people to the rally. And the church has essentially given the event its blessing."
Greece says its neighbor's name implies a territorial claim on its own province of Macedonia and its ancient heritage. But both governments say they are ready to end the 27-year deadlock before the summer, adding a modifier like "new" or "north" to the republic's name.
The proposals have triggered protests in both countries, with critics on both sides viewing the possible deal as a national humiliation.
Tens of thousands of protesters joined a rally last Sunday in Thessaloniki, Greece's second-largest city in the north of the country - though organizers said the number of people present was at least five times the police estimate of 90,000.
An organization representing Greek Orthodox clergy endorsed the Athens rally this week, while the church's leadership dropped its objections to bishops' attendance.
Western countries are keen to resolve the Macedonia dispute and promote the country's NATO membership as a thinly-veiled response to what they see as increased Russian influence in the Balkan region. Greece has vetoed Macedonia's membership of NATO and other international organizations until the name dispute is settled.
But popular opposition to a deal in Greece has put left-wing Prime Minister Alexis Tsipras under additional pressure as Greece slowly emerges from years of financial crisis. His own coalition partner in government, the nationalist Independent Greeks, opposes a compromise on the name issue.
Tsipras, who met this week with Macedonian Prime Minister Zoran Zaev, will brief Greek opposition party leaders in a series of meetings Saturday.
Costas Kantouris in Thessaloniki contributed to this report. Follow Derek Gatopoulos at http://www.twitter.com/dgatopoulos
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