MOSCOW, NOV. 30 -- Soviet President Mikhail Gorbachev cancelled a critical trip to Moldavia today after two key nationalist factions in the republic's legislature threatened to boycott his speech there.

Earlier in the day, officials said Gorbachev had to cancel his trip because of a heavy fog at the airport in Moldavia. But a spokesman in the office of Moldavian President Mircea Snegur later said the Soviet leader cancelled after learning by phone that legislators from the Gagauz minority and the ethnic Russian Dnestr region of the republic refused to attend his scheduled speech in Kishinev, the capital.

Many Gagauz, a Turkic minority, and Russians have said they want to secede from the republic, which borders Romania, and form their own republics. Last month, three people died in ethnic clashes in Moldavia.

Snegur's spokesman said Gorbachev "expressed indignation with the activities of extremists and assessed their behavior as a lack of respect." The trip was to have been Gorbachev's first official travel within the country since his mission a year ago to Vilnius, where he failed to dissuade the Lithuanians from declaring independence.

Gorbachev also faces a potential defeat in the legislature of the Russian republic, where lawmakers are discussing a bill that would allow, for the first time, private property on Russian territory.

Gorbachev favors forms of land ownership that have not been used here in decades -- stock ventures and 100-year leases for farm plots -- but he still wavers on the critical issue of private property. In a meeting Wednesday with artists and intellectuals, he said that buying and selling of private property by individuals is "inappropriate" for the Soviet Union. "People just won't accept it," he said.

But one of his key economic advisers, Stanislav Shatalin, said in an interview recently that Gorbachev "does not see private property as some kind of devil."

Russian Prime Minister Ivan Silayev told the legislators that peasants now working on state and collective farms would not be forced to buy private plots but that the new law would give them an opportunity "and even restitution" from the repressions of the past. He said that "Land for the Peasants!" was one of the key slogans of the 1917 Bolshevik Revolution, but that the principle had been "trampled."

The Russian legislature passed the land reform bill "in principle" by an overwhelming majority but will not consider the specific points, including private property, until next week.

In the past week, Gorbachev has been campaigning in various appearances for all 15 republics to sign a new Treaty of the Union that would safeguard sovereignty for the republics but retain many structures of centralized power in Moscow.

Talking to reporters in the Russian legislature, the republic's president, Boris Yeltsin, said Russia will not sign the treaty until it knows in far greater detail how the union and the republics would divide authority. The present draft provides few specifics about the republics' power in a new union.

Yeltsin, who has clashed frequently with Gorbachev over the issue of a new union, said the republics cannot meet Gorbachev's schedule of signing the treaty within two months. "It would be good if we had it signed sometime next year," Yeltsin said.

The three Baltic republics and Georgia, which are pressing for complete independence from the union, have said they will refuse to sign the treaty. Gorbachev has said that if any of the republics split off from the union, "We will have war, real war, and one that would be terrible not only for the country but for the entire world."