MOSCOW, SEPT. 10 -- The Soviet legislature was thrown into a state of confusion today when the Kremlin announced that the government would present a single plan for economic reform that reportedly combines a radical proposal with a more traditional package.

At today's opening of the legislative session, Anatoly Lukyanov, chairman of the legislature, or Supreme Soviet, announced that Prime Minister Nikolai Ryzhkov, the author of the conservative plan, would present the unified program Tuesday.

Most legislators had thought Soviet President Mikhail Gorbachev backed the more radical "500 Days" program. Written by Stanislav Shatalin, one of Gorbachev's closest economic advisers, it calls for rapid privatization of state-run businesses and transformation of the centrally controlled Soviet economy into a free-market system.

Ryzhkov, who has been under pressure from his political opponents to resign, has said a rapid transfer to a market economy that gives greater powers to the Soviet Union's 15 republics would weaken central authority and help cause the nation's collapse.

In the foyer of the Supreme Soviet today, Shatalin was clearly worried that Gorbachev, after previous vows of support, would dilute the "500 Days" program. Although Gorbachev said on Aug. 31 that he might seek to incorporate features of Ryzhkov's plan into Shatalin's, Shatalin said the two plans were, "in their essence, incompatible."

When Lukyanov announced that Ryzhkov would present the plan -- "with possibly some alternatives within the plan" -- some reformers in the gallery clutched their heads or sighed in apparent disbelief. For weeks, legislators have said they thought that Gorbachev had decided to endorse Shatalin's plan in full. Now, legislators are unsure what will be in the draft presented by the government.

Lukyanov said that Gorbachev would attend Tuesday's session of the parliament.

One of the leading reformers in the legislature, Leningrad Mayor Anatoly Sobchak, took the floor today and, speaking for the Inter-Regional Group of radical legislators, demanded a no-confidence vote on Ryzhkov. "We have no right to keep such an incompetent government in power," Sobchak said.

Before and after Gorbachev's Sunday summit with President Bush in Helsinki, the Soviet leader held lengthy meetings with his economic advisers, Ryzhkov and economist Abel Agenbegyan, who has been acting as an "independent mediator" to help fashion a coherent reform program. Shatalin said he found the meetings "a bit bewildering." In the meantime, the Soviet public, facing bread lines and worsening shortages of food and consumer goods, grows more impatient with the government every day.

Shatalin said in an interview that on repeated occasions Gorbachev has given him assurances that he will adopt the more radical "500 Days" plan and abandon the sort of centralization and economic planning that Ryzhkov insists must be retained to avoid a collapse of the Soviet Union.

Under the existing system, factories, farms and land are the property of the state, controlled by bureaucrats in various ministries and Communist Party organizations. Shatalin envisions, within just two years, the transfer of more than two-thirds of all state enterprise to private hands, either as joint-stock operations or small businesses.