NEWS ANALYSIS : Gorbachev: President Left Without a Country : Upheaval: He has brought about his own downfall, a former aide says. A showdown is scheduled for today.

Mikhail S. Gorbachev is now a president without a country.

It was wrested from him Sunday at a top-secret meeting in the forest near the Soviet-Polish frontier. In a moment of terrible irony, the land that Gorbachev tried so hard over the past 6 1/2 years to coax and shove into the modern world, he evidently ended up destroying.

The Union of Soviet Socialist Republics, the largest of the world’s nations, one-sixth of the planetary land mass, “is ceasing its existence,” the leaders of the Russian Federation, Ukraine and Belarus said.

In its place, they founded a commonwealth of independent states.

Their showdown with Gorbachev comes inside the Kremlin at high noon today, at a meeting also to be attended by the leader of Kazakhstan. Countless times, Gorbachev has displayed his canny mastery of the art of wielding power. But partisans and foes alike sense that an era in world history has come to a close.

“I can’t help sympathizing with Gorbachev at this difficult moment. But we must be frank: He has done all he could to bring about his own end,” Yegor K. Ligachev, Gorbachev’s No. 2 deputy in the Communist Party who was purged last year for his outspoken conservative views, said acidly.

Igor Malashenko, a former Gorbachev spokesman, said the Soviet leader is politically finished unless he persuades republic presidents to accept his blueprint for a Union Treaty that gives a central government responsibility over defense, maintaining a single market and coordinating foreign policy.

Without such a center, something the Russian-Ukrainian-Belarus commonwealth omits, “there will be no place for Gorbachev,” said Malashenko, now political editor for Soviet television.

Like a dynamite charge with a long-delay timer, the August attempt at a conservative coup d’etat may ironically have succeeded in demolishing Gorbachev’s leadership months after the putsch sputtered and died in the streets of Moscow.

Those tense summer days made Yeltsin the most powerful man in the country, persuaded Ukraine--the most populous and economically important republic after Russia--to secede and badly hobbled Moscow-based central bureaucracies such as the military and the KGB that had been the ribs of Soviet statehood.

All of those events were body blows to Gorbachev’s ability to maintain his hold on the country he has led since March, 1985.

To promote his cause for a single state structure, Gorbachev has plenty of arguments and was making them as today’s Kremlin meeting drew near. In apocalyptic hues, he evoked what would happen if a nuclear-equipped superpower that sprawls across Eurasia were to shatter into its ethnic components.

“We are close to the limit after which anarchy and chaos begin,” Gorbachev said Sunday in a television interview before the formation of the new commonwealth was announced. A fractured U.S.S.R., he said, would make the brutal violence in Yugoslavia seem like a “joke.”

“If the answer is no from Yeltsin to the Union Treaty, then it will be disaster, it will be civil war,” Malashenko later agreed. The Muslim and other non-Slavic peoples of the Soviet Union, he said, “will rebel against the Slavic nations.”

In today’s talks, Gorbachev will certainly try to enlist Kazakhstan President Nursultan A. Nazarbayev as his ally, and in fact, after flying to Moscow Sunday evening, a visibly worried Nazarbayev said he still believes it would be foolish “to break up our state in this most difficult time.”

Significantly, the Kazakh chief of state was not on the guest list for the weekend talks in a forest dacha that brought together Russia’s Yeltsin, President Leonid M. Kravchuk of Ukraine and President Stanislav Shushkevich of Belarus. With Soviet pundits already talking about a nascent “union of Slavic states” forming on the ruins of the old Soviet Union, Nazarbayev may want to hang onto some vestiges of the old system to safeguard his status.

In what seems like a last, desperate bid at preserving both his country and his political office, Gorbachev has called on lawmakers in the 12 republics that were part of the Soviet Union to reconsider his Union Treaty, staking his own political fate on the outcome. “If the parliaments refuse the concept of a democratic, confederate state--one state--I think the president will resign,” presidential spokesman Alexander A. Likhotal said Sunday. But it would take a Talmudic scholar to determine whether Gorbachev still has a job to resign from.

Likhotal and some others said they thought Gorbachev might be able to prolong his political career as leader of the post-Soviet “commonwealth,” with Likhotal saying the “door is still open” for such a move. But Yeltsin’s spokesman ridiculed such speculation.

“Is there a political leader of the British Commonwealth?” Pavel I. Voshchanov asked. As he knows, there is not.

In his televised comments on Sunday, Gorbachev stoutly defended the accomplishments of his nearly seven-year tenure at the helm of the Soviet state. But in light of the crushing burden of his country’s problems, he could only ask to be given more time.

“We began perestroika in order to transform the economy, our multinational state and the political process. We are moving ahead along all lines: in the economy toward mixed ownership and a market, in politics we have come to free elections and a multiparty system, competition and new ideas. We are learning,” Gorbachev said.

But the cost of the educational process has been terrible indeed. As Gorbachev spoke, tens of millions of his countrymen were worrying about finding decent and adequate food for the coming week, and about the likelihood that in the grip of a frigid December, the power or heat might fail.

Ethnic warfare and unrest have flared in the country’s southern regions. There have been rumblings about the possibility of another putsch. The Soviet state bank says it has run out of money. And as Russian television news put it, “The cause of Gorbachev’s life--the creation of a union of states--is drawing to a close.”