250,000 Urge Reform in Protest at Kremlin : Soviet Union: The momentum for change grows on eve of Central Committee meeting. Demonstrators demand an end to one-party rule.

A quarter of a million people, gathered outside the walls of the Kremlin in central Moscow, called Sunday for an end to the Soviet Union’s system of one-party rule in one of the biggest political demonstrations since the Bolshevik Revolution brought the Communists to power more than 70 years ago.

As the momentum for change gathered in advance of the meeting today of the Communist Party’s policy-making Central Committee, the protest dramatized the growing demand for more sweeping reforms in the Soviet Union’s political and economic system and the widespread impatience with their slowness so far.

The crowd waved huge white-red-and-blue flags of pre-revolutionary Russia, an emblem for what many now regard as far better times, and held placards warning party officials to “Remember Romania,” where a popular uprising overthrew President Nicolae Ceausescu’s regime only six weeks ago.

“Things cannot continue as they are,” Boris N. Yeltsin, the radical populist, told the vast crowd that had gathered in Manezh Square, across from the Kremlin. “At this plenum, the party has been given one last chance.

“It is necessary to restructure the Communist Party. There must not be a party monopoly on political power.”

This change would be so fundamental after more than seven decades of one-party rule by the Communists that virtually no other element of the Soviet political or economic system could stand without challenge.

But the sentiments at the five-hour rally were such that the country seemed to be on the very edge of changes not seen since the Bolshevik Revolution.

.j “We need a free society with a free economy . . . a society of truly free people,” Gavriil Popov, a political economist, said, telling the rally that the party leadership is hindering reforms and calling upon the party to open talks with the country’s emerging “democratic opposition” on the country’s future.

President Mikhail S. Gorbachev, the party’s general secretary, is scheduled to lay out his ideas for expanding and accelerating perestroika, as his reform program is known, when he addresses the Central Committee in the Kremlin this morning.

Speaking with a delegation of coal miners, Gorbachev said in remarks published today in the Communist Party newspaper Pravda that the party no longer claims a monopoly on power and is prepared for “a political dialogue with all those who favor the renewal of a socialist society.”

“On a principled level, our point of view is that a multi-party system is not a panacea,” he said, “but the degree of society’s democratization is of decisive importance as is the democratic nature of all its structures.”

Gorbachev is expected to propose an end to the party’s constitutionally guaranteed monopoly on political power and the acceptance of a multi-party system as a further extension of his concept of “power sharing,” according to Radio Moscow’s Interfax news service.

Sunday’s rally, which began with a march through the center of the Soviet capital, had much of the atmosphere of the rallies last autumn in Czechoslovakia and East Germany before their conservative governments fell.

Comparing the moment when the crowd, hundreds abreast, surged into the square facing the Kremlin, activist Oleg Rumyantsev, an organizer of the new Social Democratic Assn. here, told Radio Moscow, “The intensity, the emotional tension, the general joy were about the same” as that moment when the Berlin Wall was first breached. And his words were repeated and repeated and repeated on nationwide radio.

Thousands of flags and banners were held aloft in the square--those of pre-revolutionary Russia, of the independent Ukraine, of the Baltic republics of Estonia, Latvia and Lithuania, of Armenia, Azerbaijan and Georgia and of Islam--and all were shown in the extraordinary television coverage of the rally.

The marchers, chanting in unison, denounced the KGB, the Soviet security police; Politburo conservative Yegor K. Ligachev, and the Soviet army for its intervention last month in Armenia and Azerbaijan.

“Long live the beginning of the peaceful, nonviolent revolution of February, 1990!” Yuri N. Afanasyev, a leading radical, told the cheering crowd as it assembled at the end of Gorky Street, just 170 feet short of the Kremlin and Red Square.

Police blocked streets to allow the march, which had the permission of city authorities, and thousands of police and young soldiers from the internal security forces linked arms to funnel the demonstrators into the huge square.

The crowd was estimated by police at more than 200,000, by Radio Moscow at 300,000 and by Soviet television as simply “more than anyone has seen in the streets of Moscow for 70 years.”

Reporting extensively on the demonstration, Soviet television said: “Perestroika is storming through the party. The old guard is suffering blow after blow.”

But the official Soviet news agency Tass, increasingly a vehicle for conservative views, denounced the rally as “destructive” and an attempt to exert “pressure and blackmail.”

“Among the participants turned up people who take extreme positions,” Tass said, “and in their speeches they, in fact, unmasked themselves as extremists.

“They showed themselves as not concerned at all with the fortunes of perestroika and renewal but determined to use the platform of the rally to exert direct pressure on the public and the authorities.”

The mounting popular anger with the party was clearly evident, however, as the crowd cheered the most radical speakers.

“The numbers of those present today is sufficient to storm the Winter Palace and the Lubyanka,” Igor Chubal, a radical Communist, declared, referring to the Bolsheviks’ capture of the Winter Palace in Leningrad in 1917 and to the headquarters of the KGB at Lubyanka prison in central Moscow.

“If a peaceful resolution fails, we shall have to make a different one. . . . The Communist Party stands in the way of democratization. Like the Berlin Wall, it will fall if it remains such a barrier.”

The rally brought together supporters of popular fronts in Moscow and other cities, the Assn. of Moscow Voters, the Memorial, a group dedicated to remembering the victims of dictator Josef Stalin, and other reformers, and it marked a major step toward unity of what they call “the democratic opposition.”

“We have no more time,” Nikolai I. Travkin, a member of the Congress of People’s Deputies, said, calling for unity. “We do not have time for disagreements among ourselves.”

Yeltsin, a former member of the ruling Politburo and still a member of the Central Committee, told the rally that he would ask to speak at the committee’s closed-door meeting today and would propose repeal of Article 6 of the Soviet Constitution, which gives the party the “leading role” and, in effect, the exclusive right to rule.

“There must be no monopoly of power,” Yeltsin said to a thunderous roar from the crowd. “Down with the Communists!”

Nikolai Shishlin, a senior Central Committee official, meanwhile told U.S. television on Sunday that a multi-party system would emerge soon in the Soviet Union and alter the composition of the government.

“I think the political process is going in this direction, and I think that we will have a multi-party system,” he said in an interview on ABC’s “This Week with David Brinkley.”

The Communist Party has allowed the reform process to slow down, and measures are needed now to accelerate it again, Shishlin said. “Reforms will start in the party ranks because the party left behind perestroika, and just now it is necessary to reconstruct the party,” he said.

Gennady I. Gerasimov, the Soviet Foreign Ministry spokesman, explained that Gorbachev believes that the Communist Party cannot claim the leading role in the country unless it fights for it and wins in free elections.

“My guess is that in this platform, they are going to say that if the party wants to be the leading party and win the elections it must be energetic enough to fight opponents and to win in free elections,” Gerasimov told CBS’s “Face the Nation.”

Talks Broken Off. Armenians accused Azerbijanis and headed home. A10