MOSCOW, JUNE 27 -- The Soviet Communist Party has given Kremlin leader Mikhail Gorbachev the two key tools for reform he has spent two years battling for: a package of economic reforms widely considered the most radical ever introduced in the post-war Soviet Union and a team of political allies apparently with enough power to push them forward.

But at the end of a two-day meeting, the party's powerful Central Committee also left the Gorbachev leadership with the daunting agenda of enforcing reforms so controversial in communist systems that they have provoked riots and attacks from orthodox communists when introduced in other East Bloc countries.

Despite the passage of the new reforms, Gorbachev is also left to overcome a resistance so entrenched that, by his own account, it includes senior party officials appointed during his tenure.

Yet, Soviet historian Roy Medvedev today described the reforms as "the biggest, most important step," in Gorbachev's rule. Passed yesterday, they refuted a widely held view among western experts that the Kremlin leadership was unwilling to take bold enough steps to turn around faltering Soviet growth rates and a longstanding problem of poor product quality.

Western diplomats here regard the blueprint for breaking up the rigidly centralized system of Soviet economic management and other reforms passed by the Central Committee yesterday as far more radical than they had expected so early in the rule of the 56-year-old Gorbachev.

The plan to reform and eventually raise prices, one of the linchpins of the program, is viewed as particularly radical since price increases in neighboring Poland and other Soviet bloc countries have led to widespread public disgruntlement and riots.

The action appeared to have countered a sense that opposition to reforms in the ruling Politburo would water them down. By electing three new reformist-minded members, bringing the total of Politburo appointments under Gorbachev to eight, the Central Committee threw the balance of power in the 14-man ruling body behind the economic reform program.

In particular, the ascendancy to the Politburo of Alexander Yakovlev, the 63-year-old propaganda chief believed to be a key architect of the campaign for "reconstruction," has ended a phase in which Gorbachev has seemed the most outspoken member of the ruling body.

"The opposition problem in the Politburo is all but resolved," said Medvedev, a prominent Marxist historian with expertise in the reform movements launched under previous Soviet leaders.

"The remaining opponents will either join the majority, sit silent or gradually be removed," Medvedev said. In the run-up to the meeting, the 69-year-old Ukrainian party chief, Vladimir Shcherbitsky, regarded as the strongest opponent to Gorbachev in the Politburo, has adopted a conciliatory tone toward the reforms in public appearances.

With the leadership focusing heavily on the domestic economy, western diplomats expect the burden of day-to-day management decisions in the reform drive to fall on Politburo members Gorbachev, Nikolai Ryzhkov, Nikolai Slyunkov, Victor Nikonov and Lev Zaikov, all considered political progressives with expertise in either industrial or agricultural management.

Western diplomats say that the threat of opposition within the Politburo remains, however, since the eight members elected under Gorbachev include some whose longterm allegiance is uncertain. Second-ranking Politburo member and chief party ideologist Yegor Ligachev, for example, has alternately appeared to back and brake some of the key political reforms.

Also, a bid by Yakovlev to take over the ideology portfolio within the ruling body will likely lead to instability in it at least in the short term, western diplomats here said.

The meeting revealed that support for the reforms is far from unanimous within the 300-member Central Committee. Describing the atmosphere during the closed-door debate after it ended yesterday, Gorbachev aide Abel Aganbegyan said that speeches were "sharp," and that members voiced "contradictory opinions." One member said he objected to aspects of the new law on state enterprises, Aganbegyan added, but recommended passing it now rather than letting debate drag on for months.

Success in the reform drive is far from certain, however, with Gorbachev and his allies facing an uncertain reception across the Soviet Union and shortages in both locally based, reformist-minded cadres and the financial resources needed for incentives.

In his Thursday speech, Gorbachev conceded that the two years of reforms introduced so far had made an "insignificant" difference in economic performance.

Under heavy attack, the state planning ministry and key machine-building ministries could retaliate to drag out plans for decentralization.

The Gorbachev leadership is due for other major battles, too -- over plans eventually to make the ruble a convertible currency, for instance.

"We can consider this the beginning of the demonopolization of the Soviet economy," Medvedev said. "It won't be easy."