MOSCOW, SEPT. 21 -- President Mikhail Gorbachev said today that he may be forced to introduce direct presidential rule and other emergency measures in some regions of the Soviet Union in order to save his reform program.

Addressing the federal legislature, or Supreme Soviet, Gorbachev said immediate action is necessary to prevent the collapse of the economy and prevent a breakdown in law and order. He also urged deputies to grant him extensive new powers to rule by decree during the coming months in order to ease the transition to a market economy.

Constitutional amendments and new laws introduced earlier this year give the president broad emergency powers, including the right to suspend local and federal government organs, to avert threats to the country's stability. His statement today was the clearest indication yet that he may be seriously considering a temporary return to authoritarian rule in some parts of the country.

Despite Gorbachev's appeal for urgent action to tackle the Soviet Union's growing economic problems, the Supreme Soviet postponed an expected vote on an emergency package of economic measures until Monday for lack of a quorum. It has spent the past two weeks debating rival proposals for dismantling the system of central planning in favor of a market economy.

Describing the present political and economic situation as "unstable," Gorbachev said he was opposed to the introduction of a state of emergency all over the Soviet Union, saying that such a move would be "premature." However, he warned that it might be necessary to declare presidential rule in certain regions and suspend some elected institutions.

"The situation has come to the point that if it is required we must do this," the president said, pounding his fist on the table. He added that the time had come to "say firmly that this is enough and it is necessary to make decisions."

A draft resolution approved by Gorbachev endorses a radical blueprint for a transition to a market economy within 500 days as the basis for a new economic program. But it also suggests that the 500- Day Plan, as it is known, should be amended to reflect comments by deputies and the more cautious approach of the federal government headed by Prime Minister Nikolai Ryzhkov.

Gorbachev, who appears to be wavering between his political support for Ryzhkov and his conviction that drastic changes are needed in the Soviet economic system, flatly rejected calls for the resignation of the prime minister. He said that it would be irresponsible to "start reshuffling at this historic time when we have important things to do."

The Russian republic's parliament Thursday formally adopted a resolution demanding Ryzhkov's resignation and the formation of a government of national unity. Last weekend, tens of thousands of demonstrators rallied in front of the Kremlin, accusing the prime minister of acting as a brake on reform.

Gorbachev did not make clear which regions of the country might be brought under presidential rule if the political and economic situation continues to deteriorate. But he revealed that he had seriously considered imposing a state of emergency on the Baltic republic of Lithuania earlier this year after it declared its independence from the Soviet Union.

Some deputies applauded when Gorbachev said that he would have been acting within his constitutional rights had he dissolved the republic's parliament for its defiance of Moscow. He said that he had refrained from taking such a step because he "must first exhaust all other means at the president's disposal for a political solution."

Additional presidential powers now under consideration by the Supreme Soviet would give Gorbachev the right to issue decrees covering virtually every aspect of economic activity, including the budget deficit, property, wages and prices. They also would extend to the area of law and order, giving him authority to intercede in social conflicts and strikes.

As Gorbachev was addressing the legislature, his principal political rival, Russian President Boris Yeltsin, was involved in a car accident. Aides said Yeltsin was taken to a hospital suffering from minor shock after his chauffeur-driven Volga sedan was rammed in the side by a car driven by a pensioner in central Moscow.

Police said that there was nothing suspicious about today's incident, which occurred after the pensioner failed to notice a policeman holding back traffic to allow Yeltsin's car to turn left. Russia's first deputy president, Ruslan Khasbulatov, told the republic's parliament that Yeltsin had sustained heavy bruises on his right hip and a light bruise on the head.