Gorbachev Aide Assails Economic Critics : Soviet Union: Opponents are adding to political instability, eroding international confidence, he says.

Critics of President Mikhail S. Gorbachev’s economic reforms are increasing political instability in the country and eroding international confidence in the Soviet Union with their attacks, a key Gorbachev adviser said Thursday.

Abel Aganbegyan, who compiled the reform package that Gorbachev will formally present to Soviet lawmakers today, accused Boris N. Yeltsin, president of the Russian Federation, of endangering the country’s economic recovery with his denunciations of the Gorbachev program.

“Every such speech costs us tens of billions of dollars in foreign credits,” Aganbegyan said, adding that Yeltsin’s latest criticism would probably mean the loss of about $20 billion in credits Moscow is urgently seeking.

“No sensible banker would put his money in a country where there is such turmoil,” Aganbegyan said.

Yeltsin, whose radicalism seems to increase with his popularity, attacked Gorbachev’s latest reform program as a blueprint for an economic catastrophe when it was published Tuesday. He called it a further government attempt to retain control of the centralized, state-run economy rather than the promised effort to rely on market forces.

“His statement had a clearly political character,” Aganbegyan said, referring to the deepening feud between Yeltsin and Gorbachev. “From it, I could see that he had not read the (plan). He quoted figures that did not relate to anything that I know, and it is not clear where he got them.”

Warning that the country has simply run out of time for further debate on the course it should take, and that action is already overdue, Aganbegyan won approval later Thursday from the four economic affairs committees of the Supreme Soviet, the national legislature.

Gorbachev, in a speech aides are billing as “of fundamental importance,” will seek full legislative endorsement today of his plan for a two-year, step-by-step transition to a market economy.

Unlike the radical “500-Day Plan” that he had favored earlier to push the country quickly through the painful transformation, this program moves gradually, with the government relinquishing its power only as new economic institutions are built.

“The president is the main author of these guidelines,” Aganbegyan said. “There was not a group of people who worked it up for his signature; as we worked, each point was cleared with him.”

Most of the goals of the “500-Day Plan,” drafted by Stanislav S. Shatalin, another Gorbachev adviser, have been retained, Aganbegyan asserted, but the strategy to achieve it has been changed, and the timetable, intended to force rapid change, was dropped.

Overall, Gorbachev’s proposals reflect much more of the caution of Prime Minister Nikolai I. Ryzhkov--who insists that the government has a political responsibility to manage the transition--than Shatalin’s vision of a free, entrepreneurial, market-driven economy developing from the virtual destruction of the present system of state ownership, central planning and government management.

With inflation increasing sharply and unemployment rising, the country simply could not withstand the shock of the Shatalin program, Aganbegyan argued.

“I do not believe in quick stabilization,” he told the lawmakers. “The economy is in much worse shape than is commonly perceived and worse even than the statistics that are currently available show.”

To prevent hyperinflation, the central government would control about a third of all prices, especially for strategic goods and consumer staples, rather than allow them to be set by supply and demand, Aganbegyan said, and rationing will undoubtedly become the rule.