Gorbachev Blocks Attack on Leaders : Party congress: He uses his power to persuade delegates to abandon a search for scapegoats in failure of reforms. The move quells a conservative uprising.

Soviet President Mikhail S. Gorbachev halted a hunt for scapegoats in his Kremlin leadership Saturday with a display of power and political skill, reining in belligerent conservatives who accused his top lieutenants of driving the nation to the brink of ruin.

After delegates to the 28th Communist Party Congress excoriated two key reformers and voted to call each member of the leadership to personal account for the nation’s crisis, Gorbachev countered with a schoolmasterly upbraiding and an instinct for retaining control.

“If you want to bury the party, to split the party, then continue on this course,” Gorbachev reprimanded the delegates, warning them to “think, and to think hard.”

In the morning session, conservatives had pilloried Politburo members Alexander N. Yakovlev and Vadim A. Medvedev, two of Gorbachev’s staunchest supporters, accusing them of errors that have cost the Communists power and influence throughout the world.

Fired by their success in rattling the once-untouchable ruling figures, the delegates, swept along by aggressive hard-liners, voted to assess each leader’s role in the failure of reform.

The reforms, inaugurated by Gorbachev five years ago amid much promise, have not only failed to improve living standards but have deepened economic troubles and inflicted the worst food crisis since World War II on the people.

Disillusioned with the Communist Party’s inability to stem the decline, hundreds of thousands of members have quit the party, once the pinnacle of prestige and privilege.

From the outset of the congress, the nearly 4,700 delegates have held the party leadership responsible and questioned the wisdom of perestroika , Gorbachev’s program of political and economic reforms.

On Saturday, the angry delegates were able to question members of the party’s Politburo directly, triggering the first real debate since the congress opened Monday.

One after another, Politburo members were summoned to the rostrum to answer the barbed and hostile questions of delegates, and by the end of the morning the congress had voted, nearly 2 to 1, to evaluate the performance of each member of the leadership over the past four years.

Gorbachev, moving to quell this conservative uprising and the challenge it represented to his own authority, took over chairmanship of the afternoon session and persuaded the majority of loyal or uncertain delegates to vote down separate report cards in favor of a statement on the leadership’s collective guilt.

The resulting criticism in a draft resolution the congress will consider Monday is a watered-down reprimand that has spared Gorbachev and his reform team an embarrassing exposure to further hostility.

Gorbachev’s ability to control undulations of unrest among delegates who appear to be in search of an authoritative leader also was tested by repeated outbursts that disrupted speakers, including the president himself.

“I am ashamed when this hall turns into a public free-for-all,” Gorbachev said, chastising the delegates as they repeatedly challenged his maneuverings to deflect criticism and stay in command.

The decision on assessing responsibility followed appearances by five Politburo members to answer questions from the delegates, who have been meeting in the Kremlin for nearly a week.

The crowd was stirred up by Yegor K. Ligachev, a hard-line member of the Politburo, who lashed out at both foreign and domestic setbacks.

He denounced moves to increase private property and speed the transition to a market economy, winning hearty applause for a suggestion that pro-market supporters should be the first to experience the unemployment such reforms are likely to spur.

Ligachev also condemned German reunification and Baltic separatism.

“The greatest danger, comrades, comes from anti-socialist forces, from nationalists of all types, who in some republics are already restoring the bourgeois order,” the Siberian conservative railed in a clear slap against the Baltic states of Lithuania, Latvia and Estonia.

Reunion of the two Germanys was a “swallowing” of East Germany by its Western brother, he said.

Ligachev’s words fueled a controversy that has surfaced repeatedly at the congress over the departure of Eastern European allies from the Communist flock.

Foreign Minister Eduard A. Shevardnadze denied that East Germany “has been given to Bonn on a plate,” warning that security relations among sovereign states are better founded on mutual interest than military force.

“We could have blocked reunification by the use of our forces stationed in the German Democratic Republic,” Shevardnadze said. “But what that would have meant is clear to anyone. And that is the answer to anyone who says we should not have allowed it.”

Gorbachev stepped in after the thunderous applause Shevardnadze won from the delegates to suggest calling an end to the time-consuming debate over each Politburo member’s address to the congress. Winning the delegates’ support on that easily, Gorbachev ordered a 30-minute break.

Pressing ahead forcefully after the recess, he proposed a vote on collective assessment of the leadership’s responsibility, getting the decision taken earlier in the day overturned by a vote of 2,495 to 1,545.

Reform advocates said the reversal prevented the congress from giving a boost to conservatives.

“Our Russian thirst for blood is showing,” Inna Dementyeva, a delegate from Moscow, said, criticizing the effort to expose the leaders to individual account.

Delegates on Monday will consider the general assessment of top-level culpability, a draft of which was introduced by Vladimir A. Ivashko, president of the Ukraine and a member of the party’s Politburo.

The party leadership “has not realized all possibilities for its radical transformation from the state party into the political leader,” Ivashko read from the proposed resolution. “The Communist Party and party committees of all levels failed to restructure their work, to mobilize creative potential of party organizations.”

Yakovlev and Medvedev had been hounded by hard-liners in the raucous morning debate.

Yakovlev, one of the leaders responsible for foreign policy, rejected delegates’ accusations that he had contributed to the worldwide decline of socialist prestige.

“If a people turns its back on the party, it is a matter for the people,” the 66-year-old Politburo member stated.

Medvedev accused his critics of indulging in nostalgia for the uncontested power they held in the days of dictatorship.

Delegates had peppered them with biting questions about their role in democratic reforms that have led, in the view of conservatives, to a fall from grace for the party that once ruled without challenge.

The new freedom of speech encouraged by Gorbachev’s glasnost (openness) policy has brought government ministers and regional party bosses in for criticism, but few members of the party’s upper echelon have ever experienced such public rebukes.

Both Yakovlev and Medvedev, visibly rattled by the criticism, indicated they would be leaving the Politburo after the congress.

Gorbachev disclosed earlier that three other members of the ruling body had asked for retirement, and others are expected to withdraw or be removed at the end of the 10-day congress that will seat a new leadership.

Delegates have indicated they will return Gorbachev to the role of party leader, likely with a deputy to take some of the political workload off his shoulders.

Leningrad party leader Boris V. Gidaspov told reporters that two party members considered front-runners either to challenge Gorbachev as general secretary or to serve as his deputy are Russian President Boris N. Yeltsin and Ivashko, the Ukrainian leader.

The Ukrainian Parliament, meanwhile, has called home 60 of its delegates to the congress to hold a session on republic issues, another sign of assertiveness by one of the nation’s more than 100 ethnic groups.

During his appearance before the congress, Prime Minister Nikolai I. Ryzhkov said the secessionist movement in Lithuania would have to abide by Soviet law, which includes holding a public referendum and phasing the withdrawal over at least five years.

Lithuania’s Parliament voted last week to suspend its March 11 declaration of independence for 100 days, buying time to work out a solution with Moscow, which had invoked an economic embargo on the republic in mid-April.