MOSCOW, MAY 30 -- Boris Yeltsin, the newly elected president of the Russian republic, called today for rapid transformation of the Soviet Union into a loose confederation in which laws of the country's 15 constituent republics would take precedence over federal legislation.

Addressing his first news conference as leader of the largest and most powerful of the Soviet republics, Yeltsin also demanded resignation of the national government headed by Premier Nikolai Ryzhkov and denounced its plans for large price increases in transition to a market economy as "tantamount to suicide."

Yeltsin's statements appear to put him on a collision course with President Mikhail Gorbachev, who campaigned strenuously against his former protege's election before flying to North America for meetings with Canadian and U.S. leaders. They also cloud prospects for the success of the government's latest economic package, which has already run into strong public opposition and triggered panic buying.

The burly, white-haired populist politician said that the Russian legislature would try to adopt a landmark declaration on the sovereignty of the republic in time for Gorbachev's return next week. He said the document would assert Russia's right to dispose of its land and natural resources, in addition to the primacy of Russian laws.

"We hope to greet the president with a declaration of sovereignty in our hands," said Yeltsin, who was expelled from the Communist Party leadership in November 1987 after criticizing the slow pace of economic reform.

If implemented, Yeltsin's political program would change the nature of the Soviet Union radically, stripping the central government of many of its current powers and boosting the rights of the republics. The world's largest country would be transformed, in effect, into a confederation of sovereign republics, each pursuing its own foreign and domestic policies.

The most important points in Yeltsin's program, as outlined in today's press conference, included the following:

The Russian republic would conclude treaties with foreign countries and the other Soviet republics on the establishment of direct commercial and political relations. Ties with the government in Moscow would also be determined by treaty.

After a one-year transitional period, Russia would charge the other republics world prices for exports of oil, gas and other raw materials. At present, Russia sells its raw materials to the other republics at prices that are only a fraction of world levels. Such price rises would severly strain the less developed Central Asian republics, which rely heavily on imports of Russian raw materials.

Private property would be legalized in Russia for farms, small factories and businesses. All property owners, including private individuals, would have equal rights. The federal legislature has refrained from legalizing private property, which the Communist manifesto describes as a form of "exploitation of man by man."

Russia would pursue its own foreign policy, eventually seeking a seat in the United Nations. Foreign aid to Third World debtor countries would be reviewed. Such a step could result in radically reduced deliveries of subsidized Russian oil to Cuba, possibly destabilizing the rule of Fidel Castro.

Addressing Russian legislators last week, Gorbachev denounced many of Yeltsin's proposals as populist demagoguery, insisting that they could lead to the breakup of the Soviet Union. He accused Yeltsin, a former member of the Communist Party's ruling Politburo, of abandoning the "socialist course" pursued by Russia since the 1917 Bolshevik revolution.

Yeltsin's attempt to assert the primacy of Russian legislation is likely to lead to a constitutional confrontation between the Russian legislature and the Kremlin leadership headed by Gorbachev. The Soviet president has been embroiled in a constitutional dispute with the three Baltic republics since they adopted sovereignty declarations as the first step toward independence more than a year ago.

Any determined move by Russia toward sovereignty is likely to present even more serious problems for Gorbachev than the secession challenge posed by the small Baltic states. Stretching across 11 time zones, the Russian republic, or federation, is twice the size of all the other republics together, and its population is greater than that of all the others combined. It produces 90 percent of the Soviet Union's oil supplies, 76 percent of its natural gas and 89 percent of its hard-currency earnings.

Yeltsin served notice today that Russia might be forced to make use of its constitutional right to secede from the Soviet Union if Gorbachev blocked the attempt to promote its sovereignty. "The union leadership should recall that such a possibility exists, even if we are not looking for secession. Therefore they should look for compromise with us, not confrontation," he said.

Yeltsin, who was plucked from relative obscurity by Gorbachev in 1985 to work in Moscow, also called for direct election of the Russian president within two years in place of the present system of indirect, or legislative, election. Such an election would endow him with greater popular authority than his present position as chairman of the Russian legislature, a post which gives him the honorary title of president.

Despite repeated questioning by journalists, Yeltsin refused to clarify precisely how he intends to introduce radical economic change without the massive price rises proposed by the Soviet authorities. Most Western economists do not believe it is possible for the Soviet Union to move toward a market economy without bringing prices into line with real costs and closing unprofitable factories.

Rejecting the Polish variant of economic "shock therapy," Yeltsin said he was in favor of market-oriented reform that would not harm the living standards of ordinary Soviet workers. He was vague about how he would achieve such a goal, other than saying that higher revenues from Russian oil and gas would help cushion the shock of economic hardship.

Yeltsin said that a package of economic reforms adopted by the Soviet government last December had failed to produce positive results and that a new package now under discussion by the national legislature was scarcely an improvement. "The government must resign," he declared, insisting that the proposed price reforms were both unpopular and impossible to implement.

Gorbachev has spoken in scathing terms of Yeltsin's plans to give district councils the right to overrule republican bodies, which in turn would have the power to overrule the federal government. He said last week that Yeltsin's proposal to reverse the traditional pyramid of Soviet power could lead to "anarchy and parochialism," reducing the principle of sovereignty to absurdity.

Yeltsin said that the Russian legislature should conclude treaties with the Baltic republics as a "matter of priority" but sidestepped a question about breaking the economic embargo imposed by Moscow on Lithuania. The Lithuanian government has sent emissaries to Moscow to try to establish direct trading links and acquire sufficient oil and gas to prevent economic collapse.

"We have to move away from the previous formula of everything subordinated to a strong center. Our state, our country, will only be strong if the republics are strong," he declared.

Under Yeltsin's proposals, the center would retain responsibility for defense, state security, some foreign policy issues and coordination of the policies of the 15 republics.