Police were cordoning off Red Square and two dozen armored personnel carriers were sighted Wednesday at a military base near the center of Moscow on the eve of a planned pro-reform demonstration.

Many fear the protest will be broken up by force.Vice President Gennady Yanaev, KGB chief Vladimir Kryuchkov and Interior Ministry Boris Pugo summoned a Moscow City Council official and two organizers of the march Wednesday to warn them the demonstration could lead to "possible public disorder," the official Tass news agency said.

Anxiety over the prospect of a major confrontation had been raised by the Kremlin's announcement Monday that it was banning rallies until mid-April and by President Mikhail Gorbachev's transfer of the authority of the city police force to the national Interior Ministry Tuesday.

Tass said the Soyuz group of legislators had demanded that Gorbachev use emergency powers to end the country's political and economic crisis. They also called for him to appear at a special session of the national congress to defend his performance.

The anti-Communist Democratic Russia coalition said it expects 500,000 people to turn out for Thursday's demonstration to protest attempts to oust Gorbachev's political rival, Boris N. Yeltsin, from the chairmanship of the Russian republic's parliament.

Moscow's reform-minded city leaders, who have given permission for the rally, appealed to the nation's Constitutional Oversight Committee to rule the Kremlin ban on demonstrations unconstitutional.