President Mik-hail S. Gorbachev, struggling to maintain central control over Soviet political and economic life, plans to transform 550 armament factories to civilian production, his spokesman said Friday.

Gorbachev and top aides met to complete the conversion plan as representatives of seven Soviet republics agreed to bypass central authorities in working out a new system of economic and political cooperation.The Supreme Soviet parliament has been unable to pass a cohesive reform plan, and on Monday granted Gorbachev extraordinary powers to transform the national economy from a planned to a market system.

Representatives of nine of the 15 Soviet republics and the mayor of Leningrad, dissatisfied with Gorbachev's reforms, met in the Estonian capital of Tallinn and signed a protocol establishing an Economic Consultative Committee to coordinate their own shift to a market economy.

Another group of reformers, led by Moscow Mayor Gavriil Popov, held a news conference in the capital to express concern about the powers granted to Gorbachev.

They said in a statement they also feared "the dangerous situation created by the capitulation of the president to conservative forces, the worsening of relations between the center and the republics, especially Russia," which is taking the lead in the reform drive.

The radical Moscow Group of Deputies and Interregional Group of Deputies, consisting of reformists in the national, Russian and Moscow city legislatures, also appealed for creation of a parallel body to the official parliament as a means of hastening political reforms.

The Communist Party newspaper Pravda on Friday condemned such calls, accusing the reform group of seeking "the elimination of CPSU (Communist Party of the Soviet Union) from the political arena." Popov and other radicals left the party last July.