Soviet Official Defends Cautious Economic Plan : Reform: Gradual changes are the only way to avoid chaos, prime minister says. But Moscow mayor renews call for the government’s resignation.

Soviet Prime Minister Nikolai I. Ryzhkov, defending himself against mounting criticism that he is too conservative at a time when the country needs radical change, appealed on Saturday for public support for his program of gradual reform as the only way to avoid economic chaos and collapse.

Ryzhkov, speaking on national television amid almost daily calls for his resignation, said that a radical reform program now before the country’s lawmakers and winning popular acceptance would bring higher prices, widespread unemployment and bankruptcy for many enterprises.

“I favor averting chaos in every sphere of our country’s life,” he said. “I favor securing social guarantees to protect our people. We must not give into the shock therapy spoken about so much; we should advance more rhythmically.”

Ryzhkov also argued that the country’s economic problems are so severe that they would slow, if not undercut, virtually any reform program, including his own plan of gradual transition to a market economy as well as the rival plan, based on a 500-day timetable ending central planning and state economic management.

And, challenging the radicals in a test of political strength, he again said that if the Supreme Soviet, the national legislature, has lost confidence in his government, it can appoint a new one.

“The Supreme Soviet nominated us, and if the Supreme Soviet trusts us, the government will continue its work and fulfill its functions,” the prime minister said. “If it does not, the Supreme Soviet has the opportunity, as they say, to ‘make a decision.’ ”

Gavriil Popov, the radical mayor of Moscow, nonetheless renewed his call for the government’s resignation and announced that a mass rally would be held today outside the walls of the Kremlin to demand more sweeping economic changes than those proposed by Ryzhkov.

“We are tired--tired of empty shelves and devalued money,” Popov said in an interview broadcast on national television. “We do not want any more crises, neither the cigarette crisis nor the soap crisis. . . . In general, we cannot live like this any longer. This is the reason we are coming out in the streets. We want to change the situation.”

Popov, one of the country’s leading economists, said the Ryzhkov government “did not have, does not have and does not want to have any real plan for a transition to a genuine market economy because it is opposed to a true market.”

Ryzhkov said the Council of Ministers, which he heads, had reviewed its reform proposals on Saturday and, after comparing them with those of the radicals, believed them to be the correct course.

“The most important thing is to forecast the consequences of this or that move,” he said. “This concerns the lives of our 300 million people. We cannot help but discuss these issues, and they will have to be discussed another 10 times before we make a final decision.”

The radicals’ proposals to close unprofitable enterprises, he continued, would throw millions of people out of work.

In the coal industry alone, 120 of the country’s 500 mines would have to be closed on Jan. 1 even though they employ 270,000 workers and produce 100 million tons of coal a year, Ryzhkov said. Closing these mines would be “a very dangerous decision,” he said.

In agriculture, about a quarter of the country’s 60,000 state and collective farms can operate only with government subsidies, which the radicals plan to end. “We are for resolving this problem, too, but this has to be done step by step,” Ryzhkov said. “This should not be done overnight or in 100 days.”

Ryzhkov described his own reforms, now widely criticized, as “moderately radical” and said they are “not separated from life.” He said he had asked President Mikhail S. Gorbachev, who has backed more radical measures, for the authority to maintain the country’s present economic framework through 1991 as the basis for any reforms.

“The situation in the economy has become worse recently,” he said. “This cannot but affect the people’s mood and their attitude toward the government. The government can and should be criticized. But this criticism sometimes is simply fierce and exceeds the limits of proper relations between people.

“Some may not be satisfied with the government’s political line, but I always stand for the preservation of our state and for ensuring that the low paid, the pensioners and the students do not suffer as a result of the transition to the market. I am against ‘shock therapy.’ Some may not be satisfied and think we are not sufficiently radical. I cannot agree when we are blamed for conservatism. Our moderate radicalism is what the country needs today.”