UNITED NATIONS - The stocky moon-faced figure with the signature port-wine birthmark on his forehead settled into the armchair of his Manhattan hotel room, extended his hand and barked a hearty welcome.

"Call me Mikhail," he said.

Without prompting, Mikhail S. Gorbachev told how he learned that friendly greeting from his sworn ideological rival, Ronald Reagan, in a moment of tension-thawing familiarity two decades ago - a moment that probably helped transform the world.

"I remember the episode when we were sitting down together, President Reagan and me, and he said: 'I think the time has come for us to be on a first-name basis. Call me Ron.' "

The anecdote recalled a time when Mr. Gorbachev, the general secretary of the Communist Party and first executive president of the Soviet Union, commanded the world's attention for introducing glasnost (openness) and perestroika (restructuring) to the Soviet Union.

Historians who credit Mr. Reagan with bringing about the bloodless defeat of the Soviet Union and the end of the cold war usually note the essential partnership role played by the liberalizing Mr. Gorbachev. His burly presence is consequently one that prompts fond memories in the West, and as he moved about the streets of New York and the lobbies and corridors of the Plaza Athénée Hotel earlier this month, he stirred Hollywood-style commotions. Chesty men with earpieces cleared his path while onlookers reacted with delight and surprise, elbowing companions to point him out.

With a smile continually playing across his lips, Mr. Gorbachev is quick to make topical jokes. "That's a pre-emptive strike," he commented with glee when an American tried to interrupt him.

If he appears to embrace this adulation with particular appreciation, it may be because the bear-hug response is so different from the one he gets at home in Moscow. There, though a Nobel Peace Prize winner, he is still a public pariah, widely blamed for ushering in reforms that led to a decade of political and economic instability. In a disastrous run for the presidency in 1996, he attracted less than 1 percent of the vote.

His English-speaking aides and security people refer to him for ease and anonymity as Mr. Green, a telling code name because Mr. Gorbachev has decided to devote what he calls his post-presidential years to campaigning for the protection of the environment.

After attending Mr. Reagan's funeral in June, Mr. Gorbachev was back in the United States this month to promote Green Cross International, the Geneva-based organization he founded after the 1992 Earth Summit in Rio de Janeiro, and its American affiliate, Global Green USA.

The groups' focus is on safely eliminating unconventional weapons, stemming climate change, reducing the use of nonrenewable resources and preventing conflicts over fresh water.

Asked why he had chosen the environment as his late-life mission, he harked back to his farm background and early acquaintance with nature, as well as his experience witnessing reckless land use by the mining industry during his years as a provincial governor in Stavropol.

"Then when I became a member of the Soviet leadership," he said, "many of our achievements for me lost their luster because I learned the environmental price we had paid for them.

"We had built many hydroelectric power stations and they produced a lot of energy, but they were a blow to our land and they created reservoirs that flooded vast territories of arable land and villages. We saw the steeples of the former churches sticking out above the water, and they looked to me like funeral crosses." Now that Russia has moved toward ratifying the Kyoto treaty on climate change, Mr. Gorbachev faults the Bush administration for not doing the same. "It is very bad, very sad whenever the United States doesn't take an active stand," he said.

He also criticizes President Bush on Iraq. "The crisis in Iraq has been a lesson, and I believe that lesson has been learned by both the United States and all of us," he said. "That lesson is that unilateral action is really not the way to go, is really not the way forward."

He is respectfully critical of President Vladimir V. Putin, saying the world should support his campaign against terrorism but proposing a compromise solution to the problem of Chechnya. "Continual instability in the Caucasus will affect everybody," he said.

Mr. Gorbachev, who as Soviet leader ended a decade-long war in Afghanistan by pulling out his army, said Mr. Putin should seek to end the separatist insurgency in Chechnya by granting the largely Muslim region autonomy. "My formula for a solution is: Chechnya is part of Russia, all of Russia should help Chechnya rebuild, and Chechnya should have a special status within Russia," he said.

Now 73, Mr. Gorbachev still speaks with the brusque jollity that first gained him the confidence of Western leaders like Mr. Reagan and Prime Minister Margaret Thatcher, who, after meeting him in London, told the American president, "I think this is a man we can do business with."

He punctuates his animated speech with outstretched arms and hands that are constantly in motion, while the interpreter at his side lays a succinct English soundtrack on top of his robustly enunciated Russian.

His reminiscences often begin with the phrase "Raisa and I," a reference to his wife, Raisa Gorbachev, who broke Kremlin tradition by sharing the spotlight during his leadership. She died of leukemia in a German hospital in 1999, at 67, and Mr. Gorbachev won back some sympathy from his fellow Russians for the faithful vigil he maintained by her bedside and the visible emotion he showed at her death.

He vents his anger at how he ended up snubbed in his own country by attributing the public disenchantment to the performance of Boris N. Yeltsin, who succeeded him in office in 1991. "Boris Yeltsin spent 10 years trying to stomp out everything that Gorbachev had done," he said. "Whatever some people say or write, whatever they're trying to attribute to Gorbachev, I think I am paying for the mistakes of others."

"It was an assault, an attack on everything," he said of Mr. Yeltsin's approach. "Everything was destroyed. All they had in the end was a lot of broken furniture, and many people believe that perestroika was to blame, but those two things should not be linked. That it happened after perestroika does not mean that it happened because of perestroika. What happened after perestroika is for others to take the blame."

If he is resentful that he enjoys far more popularity outside of Russia than inside the country, he is resolute in not showing it.

"Whatever some people say or write, whatever they're trying to attribute to Gorbachev, that never shook my conviction," he said. "I'm convinced that a place in history will be available for me."

Copyright 2004 The New York Times Company