MOSCOW, JUNE 12 -- Soviet leader Mikhail Gorbachev is planning a major assault on the power of the state's central planning authorities with an economic reform program that also proposes changes in pricing, credits and management practices.

The decentralization program -- radical by Soviet standards -- was unveiled today by the state news agency Tass. The measures were discussed at an apparently stormy meeting of the nation's economic managers Monday and Tuesday in the Kremlin and will be considered at a meeting of the Communist Party Central Committee later this month. They are due to be in place by next January.

Gorbachev, in a speech later this week, spoke openly of the "sometimes polemical" exchanges on the issues, but he noted that the gathering was unanimous in supporting the need for change.

"It is the sole real alternative to the condition in which our society found itself, especially its social and economic sphere," he said. "I didn't hear any other proposals from the participants in the meeting: Everybody is for restructuring."

Many elements of the "new integral system of economic management" were left unclear in the Tass reports, and some apparently are still the subject of heated discussion. For instance, Gorbachev said new laws on the central agencies will have to be debated further and "probably much will be said."

The most concrete element in the next stage of reform is a new law on state enterprises, introduced in January and designed to redefine industrial and management relations within the Soviet Union's planned economy.

The law, heavily criticized by reformers as a self-contradictory compromise measure, was defended by Gorbachev as a "good basis for launching work to introduce into practice the new mechanism of management."

This lukewarm praise for the draft law suggested that Gorbachev has shifted the focus of reform to the overhaul of the central planning agencies and ministries, the target of a recent spate of harsh articles in the Soviet press.

In his address to the meeting, Nikolai Slyunkov, party secretary in charge of economic administration, said the power of the center had to be overhauled, noting that the central ministries' "day-to-day control over enterprises" should end. He said the work of the central agencies "will be restructured in accordance with changes in the economic mechanism."

Slyunkov also said plans exist "to change drastically the practice of price formation, make prices consistent with socially required outlays and increase their stimulating effect."

Credit policy also will be reformed to keep failing enterprises from relying on state handouts, he said. Other changes will be proposed to give local factories more autonomy and responsibility for such costs as land and water.

The powerful central agencies -- most prominently Gosplan, the state planning committee -- and the giant Moscow-based ministries have been criticized for interfering with existing reforms, protecting their power and clinging to bureaucratic techniques. The Soviet Union's rigid and often absurd pricing policies also have come under harsh public attack.

The meeting of economic managers this week confirmed the problems faced by Gorbachev's initial round of reforms, which he acknowledged are "running into difficulties and contradictions."

In his opening remarks, Gorbachev noted that earlier reform efforts had failed because "we had begun at the top." Instead of redistributing power and responsibility down to the factories and enterprises, "the higher echelons grabbed everything," he said. "No cardinal measures were thus possible."

This time, Gorbachev indicated, the same mistake will not recur. "One thing is clear already, that the law on the enterprises will not start operation unless we resolve questions of running the economy from the center," he said.

In the excerpts released by Tass, Gorbachev said the transition would go through several stages, the first ending with the current five-year plan in 1991.