PRESIDENT Mikhail Gorbachev says the Soviet Union will take a giant step on the road to recovery when the leaders of three powerful republics sign the new union treaty tomorrow.But other influential Soviet leaders, including Prime Minister Valentin Pavlov, have attacked the treaty, saying it could exacerbate problems in the country. The agreement will drastically alter the relationship between the Kremlin and the Soviet Union's 15 republics, distributing significant decisionmaking authority to the republican governments. After three arduous months of negotiation, the leaders of the giant Russian Federation, along with the Central Asian republics of Kazakhstan and Uzbekistan, will be the first to sign the treaty at a Kremlin ceremony tomorrow. Six other republics have indicated they will sign later, but one, the Ukraine, is balking at the proposed time frame. The six remaining republics - Moldavia, Georgia, Armenia and the three Baltic states, Lithuania, Latvia, and Estonia - are seeking independence from the Soviet Union and have refused to sign the new treaty. Armenia, however, may change its position depending on the outcome of a referendum in September. The republics that don't sign the new treaty will still be bound to Moscow by the 1922 union treaty. The new treaty's text doesn't contain the word "socialism" but transforms the Union of Soviet Socialist Republics into the Union of Soviet Sovereign Republics. Perhaps most important, the republics are given control over their economic resources. The treaty also allows the republics to collect taxes, then pass on a fixed percentage to Kremlin coffers. The central government will retain control over security and defense, but the republics will have a voice in military policy and foreign economic relations. The treaty's completion provides the impetus for further reforms of the Soviet Union's fast-sinking political and economic system, including a new constitution and fresh elections at all levels, according to Mr. Gorbachev. "The treaty creates the prerequisites for profound changes for the better in all spheres of public and state life," he said in a recent nationwide television address. Though less enthusiastic about the treaty than Gorbachev, Russian Federation President Boris Yeltsin is supporting it. "We favor the signing of the union treaty, although we are not quite satisfied with those provisions based on compromise," said Mr. Yeltsin, a former bitter political rival of Gorbachev, at a news conference Saturday. Other influential leaders from across the political spectrum are gloomy about the treaty's ability to heal rifts and get the country going again. The chief complaint is that the ambiguous language in the treaty could cause confrontation among the Kremlin and the republics in the future. Yuri Afanasyev and other leaders of the Democratic Russia movement have suggested that the treaty signing be put off until the "contradictory and fuzzy" language in the pact can be clarified. Many reform advocates are wary of Gorbachev's intentions and fear he may try to manipulate the treaty to retain central control. Liberals worry that hard-liners in the Communist Party could exploit the treaty to stop reform. "Party leaders are getting rid of the democratic wing and are preparing to take social revenge and stage a party and state takeover," said Alexander Yakovlev, a chief architect of the perestroika (restructuring) program, who was expelled from the party last week. Mr. Pavlov, who stands to lose a large portion of his powers, said chaos would result if the central government loses authority over the economy. And on Saturday, the Soviet Cabinet said the treaty was severely flawed because it failed to define how food and energy supplies would be distributed and utilized. "Each republic will have to tackle those extremely complicated problems by itself, while most of the republics are not prepared for it," the official Tass news agency commented on the Cabinet's position. In addition, Viktor Gerashchenko, president of the state bank, last week said the treaty could ruin the national economy, causing the collapse of the ruble. An effective national monetary and credit policy is virtually impossible because of a treaty provision calling for consensus among the republics on all financial decisions, Mr. Gerashchenko said. Such a clause allows one republic to block any economic policy decisions, he added. The central government is no longer in a strong position to resist the push to redistribute power, however. Recently, republics have been concluding bilateral treaties, such as the pact signed Saturday between Russia and Kazakhstan, and replacing Moscow as the chief overseer of economic affairs. A similar agreement was signed earlier last week by the five republics of Central Asia - Kirghizia, Turkmenia, Tadjikistan, Uzbekistan and Kazakhstan - seeking to unite the region's economies to help the transfor mation from the centrally planned system to the market. Central Asia is the Soviet Union's most impoverished area and has long suffered from the Kremlin's economic dictates.