AFTER weeks of preparation, a group of prominent Soviet liberals led by former Foreign Minister Eduard Shevardnadze announced on July 1 the formation of a new reform movement to rival the ruling Communist Party.The organizers fell short of their goal to unite the existing, fractured democratic opposition parties into one organization. They settled instead for the formation of a "Democratic Reform Movement," which will hold a founding conference in mid-September to decide its plans. Mr. Shevardnadze told reporters that he hoped to transform the movement into a new parliamentary-type party at that point. The liberal founders include a number of prominent reform-minded Communists who say they will not leave the party. Their aim is to split the party, dividing those who support the reform policies of Soviet President Mikhail Gorbachev from conservative opponents of such change. "We count on the support of the reformist wing of the Communist Party of the Soviet Union [CPSU]," the declaration of the new group stated. Mr. Gorbachev sent a positive resonse to the announcement. "It is clear the movement does not have a confrontational character and invites the cooperation of all parties and movements that support perestroika and wish success to it," presidential spokesman Vitaly Ignatenko told reporters on July 2. "If it coincides with declared objectives, we can do nothing but welcome it." In recent days, divisions within the party have been evident, with statements from conservatives in Siberia openly calling for Gorbachev's ouster as party general secretary. The party's Central Control Commission met last week to warn mostly conservative factions that their anti-Gorbachev activity violates party rules. A meeting of the party Central Committee is planned for later this month and promises to be a stormy affair. "The party is not a monolith any longer," acknowledged deputy party leader Vladimir Ivashko to reporters on Monday. "There are cracks in the party." The party leader appeared to be bidding to keep the Communist reformers within the party's ranks, disassociating the party leadership from a move to expel Shevardnadze for his activity in forming the new movement. The movement advertises itself as the actual bearers of Gorbachev's policies of perestroika (restructuring) and glasnost (openness) which began in 1985. Their statement of principles includes protection of individual rights, parliamentary politics, radical transformation of the economy into a market-based system including private property, demilitarization of the society and economy, opposition to extreme nationalism, and support for a looser but united Soviet federation. Among the nine signees are some prominent former or current advisers to Gorbachev. Aside from Shevardnadze, who resigned his post in dramatic fashion last December warning of the threat of "dictatorship," the list includes Alexander Yakovlev, considered the father of glasnost; economists Nikolai Petrakov and Stanislav Shatalin, Gorbachev's advisers until early this year; and Arkady Volsky, a Gorbachev confident who heads the power Scientific and Industrial Association, which groups pro-reform senior mana gers of Soviet state-run enterprises. Russian President Boris Yeltsin is not among the backers, but he has long insisted that he wants to be "above" party. A number of his closest political supporters, however, are among the founders, including Russian Prime Minister Ivan Silayev, Russian Vice-President Alexander Rutskoi, who heads a reform Communist faction in the Russian parliament, and Gavril Popov and Anatoly Sobchak, the radical mayors of Moscow and Leningrad. In recent interviews, Shevardnadze has argued for a new political organization. "What I stand for ... is to build a well-balanced, two-party system in our society," Shevardnadze told the independent news agency Interfax. "Whether the CPSU splits or not, we need a constructive opposition that would exist parallel to it.... They would criticize the state and cooperate with it, offering the country their solutions." Shevardnadze explained that the decision to hold off on forming a party was motivated in large part by a desire to bring liberal Communists into their fold. "If we set up an alliance, not a party, that would enable all the democratically minded people to take part in the movement.... If we set the condition of leaving the Communist Party or any other party, we'd face people with a choice and probably scare away some democratic people." The reaction of existing opposition parties has been less than enthusiastic to the new formation. The left-wing Social Democratic Party and Republican Party of Russia, which met over the past weekend, balked at the idea of dissolving themselves into a new "super-party" in which they would become "factions." "The political spectrum of the opposition is too wide to be fitted into one tight party," Republican Party leaders stated, according to press reports. They also object to forming the party as an all-Soviet party, saying this will alienate democratic movements in the republics which prefer republic-based parties. The Democratic Party of Russia, the largest existing opposition party led by Nikolai Travkin, was one of the sponsors of the move to form a new broad party. But at the last minute, according to reports here, Mr. Travkin backed off from signing the declaration. Travkin favors creation of a strong, well-organized party to take on the powerful organization of the Communists.