MOSCOW, SEPT. 17 -- Soviet President Mikhail Gorbachev called today for a nationwide referendum on whether to allow private ownership of land, a practice that would violate one of the fundamental principles of communism.

Addressing the Soviet legislature, which is debating how best to organize a transition from state economic planning to a market-driven system, Gorbachev said that the decollectivization of land is too important a decision to be left to a small group of politicians.

"The question of whether there should be private ownership of land is the sovereign right of the people to decide, and it can be decided only by a referendum," he said.

Enabling legislation to hold referendums, a novel political concept here, has not yet been presented to the legislature, however, and a high Soviet official said it could take at least six months to organize a nationwide ballot.

Gorbachev also reiterated his support for Premier Nikolai Ryzhkov, who has come under growing pressure to resign because of his opposition to radical economic reform. Gorbachev said that a political reshuffle "would draw us into grim political battles and enhance confrontation in society."

Gorbachev's call for a referendum on land ownership appeared designed to blunt charges by Communist Party hard-liners that he is presiding over the abandonment of socialism in favor of capitalism. A nationwide vote endorsing the principle of private property would undercut the position of Marxist ideologues who argue that the gains of the 1917 Bolshevik Revolution are being frittered away one by one.

In his speech today, Gorbachev seemed eager to blunt the notion that the Soviet Union is moving toward capitalism. But his surprise proposal also illustrates the intense confusion that surrounds the attempt to produce a coherent economic reform program by Oct. 1. In a dramatic departure from the secrecy that shrouded past Kremlin intrigues, the president's closest advisers have been publicly feuding over how to rescue the Soviet Union from its growing economic crisis.

Gorbachev himself has expressed general support for a radical program already adopted by the legislature of the Soviet Russian republic, known as the "500 Day Plan," that would denationalize 80 percent of the Soviet economy by the end of the decade. But he has refrained from taking a clear-cut position on specific issues, leaving himself free to continue political maneuvering between rival factions but leaving himself open to charges of indecision.

The proposal for a referendum on land ownership caught off guard and dismayed some of Gorbachev's own advisers. The principal author of the 500 Day Plan, Stanislav Shatalin, who is also a member of Gorbachev's presidential advisory council, said it would take at least six months to organize a referendum.

"If all our lives we make the most important decisions by referendum, then we're not truly assuming responsibility. It's not the way politicians should talk," Shatalin told members of the legislature.

Under constitutional amendments adopted earlier this year, the right to order a referendum rests exclusively with the legislature's parent body, the 2,250-member Congress of People's Deputies.

Another Gorbachev adviser, economist Abel Aganbegyan, warned today that the Soviet economy is in such a "catastrophic" state that further delays would be disastrous. He told the legislature that the shortages, inflation and social disorder now afflicting the country are "a joke compared with what could happen" in the future.

Aganbegyan, who heads a commission that has been attempting to find common ground between the rival plans for economic recovery, said that the Soviet Union's financial problems were compounded by a sharp drop in oil output. He predicted that the country could lose $10 billion over the next two years if oil production continues to fall at the present rate.

According to the latest official figures, industrial output in August fell by 1.7 percent from a year ago, with oil and coal output down by 8 percent. But Aganbegyan said that the real situation is "much worse than it appears on the surface."

"When you look at the situation, you should not just look at the fall in output in the past months, you should look at the trend," he said.

The 500 Day Plan would allow farmers and other private citizens the right to own land and pass it on to their heirs, a striking departure from the Communist Manifesto, which states that private ownership of property is tantamount to the "exploitation of man by man." But the plan is vague on whether landowners should have the right to resell their property on the open market.

The Soviet legislature is due to wind up its debate on economic reform Friday. Leaders of the Russian republic, which forms three quarters of the Soviet land mass and accounts for 50 percent of the population, insist that they will implement the 500 Day Plan beginning Oct. 1, even if the Soviet legislature is still deadlocked.