Soviet leader Mikhail Gorbachev today pledged "truly historic" transformations of the Soviet economy at the unveiling of his blueprint for the nation until the year 2000.

Speaking before a closed session of the Central Committee of the Communist Party, Gorbachev pledged that in the next 15 years, the Soviet Union will increase almost two-fold its national income and industrial output and that labor productivity will rise by as much as 150 percent.

These promises were among the few details disclosed today as Gorbachev presented the party elite with the drafts of a new edition of the party program, new party rules and the next five-year plan for the Soviet economy -- three key documents that will determine the tone and substance of Gorbachev's first years in power.

The documents will be circulated to local organizations for comments before appearing in the press.

Gorbachev's report on the draft proposals reflected the sense of urgency that has been evident in the buildup to next February's Communist Party Congress.

More changes in the party's top hierarchy were approved today at the plenary session of the 300 members of the Central Committee.

Nikolai Tikhonov, 80, who late last month retired as prime minister, today lost his post on the Politburo, bringing the number of full members of the ruling group down to 12, only three of them viewed as holdovers of the generation associated with the late Leonid Brezhnev.

Nikolai Talyzin, yesterday named head of the state planning agency or Gosplan, was elevated to candidate Politburo member, adding new clout to a position that had already been strengthened by the title of first deputy prime minister.

In his report today, read in full on the evening news, Gorbachev expressed his impatience with lingering opposition from the party's old-fashioned leaders.

"Not all of our cadres have given up inertia, old patterns," Gorbachev said. "Not all turned out to be psychologically prepared for work under new conditions."

In his broad outline of the new party program, Gorbachev hewed closely to the maxims of Marxist-Leninst theory and emphasized the continuity linking it to the party's past.

In the international arena, Gorbachev said the revised program would spell out a "more precise definition" of policy directives, but on the whole, his remarks repeated the usual policies of support for anti-imperialist struggles and warnings against "the very dangerous turn" in the policies of major capitalist powers.

On the domestic front, the Gorbachev report avoided the sweeping promises made by Khrushchev.

But Gorbachev still set out ambitious goals, calling for "transformations of a truly historic scale -- the implementation of a new technical reconstruction of the economy."

The five-year plan, the Soviet Union's twelfth, to run from 1986 to 1990, was revised earlier this year after it was rejected by the Politburo.

Gorbachev today referred to problems with the plan when he said work on it "did not proceed easily or smoothly."

Without providing details, Gorbachev said the new plan would call for the "structural reogranization of the economy," with special emphasis on capital investments, technical re-equiping and reconstruction of existing enterprises and speeded-up development of machine-building, chemical, electronic and electrical engineering industries.

"In short, a marked change toward greater efficiency is being laid in the 12th five-year plan," he said.