MOSCOW (AP) - Mikhail Gorbachev, who set out to revitalize the Soviet Union but ended up unleashing forces that led to the collapse of communism, the breakup of the state and the end of the Cold War, died Tuesday. He was 91.

Gorbachev died after a long illness, according to a statement from the Central Clinical Hospital in Moscow. No other details were given.

Though in power less than seven years, Gorbachev unleashed a breathtaking series of changes. But they quickly overtook him and resulted in the collapse of the authoritarian Soviet state, the freeing of Eastern European nations from Russian domination and the end of decades of East-West nuclear confrontation.

U.S. President Joe Biden called Gorbachev a “man of remarkable vision” and a “rare leader” who had “the imagination to see that a different future was possible and the courage to risk his entire career to achieve it.

“The result was a safer world and greater freedom for millions of people,” Biden said in a statement.

“Hard to think of a single person who altered the course of history more in a positive direction” than Gorbachev, said Michael McFaul, a political analyst and former U.S. ambassador in Moscow, on Twitter.

His decline was humiliating. His power hopelessly sapped by an attempted coup against him in August 1991, he spent his last months in office watching republic after republic declare independence until he resigned on Dec. 25, 1991. The Soviet Union wrote itself into oblivion a day later.

A quarter-century after the collapse, Gorbachev told The Associated Press that he had not considered using widespread force to try to keep the USSR together because he feared chaos in the nuclear country.

“The country was loaded to the brim with weapons. And it would have immediately pushed the country into a civil war,” he said.

By the end of his rule, he was powerless to halt the whirlwind he had started. Yet Gorbachev may have had a greater impact on the second half of the 20th century than any other political figure.

“I see myself as a man who started the reforms that were necessary for the country and for Europe and the world,” Gorbachev told the AP in a 1992 interview shortly after he left office.

“I am often asked, would I have started it all again if I had to repeat it? Yes, indeed. And with more persistence and determination,” he said.

Gorbachev won the 1990 Nobel Peace Prize for his role in ending the Cold War and spent his later years collecting accolades and awards from all corners of the world. Yet he was widely despised at home.

Russians blamed him for the 1991 implosion of the Soviet Union - a once-fearsome superpower whose territory fractured into 15 separate nations. His former allies deserted him and made him a scapegoat for the country’s troubles.

Gorbachev never set out to dismantle the Soviet system. He wanted to improve it.

Soon after taking power, Gorbachev began a campaign to end his country’s economic and political stagnation, using “glasnost,” or openness, to help achieve his goal of “perestroika,” or restructuring.

In his memoirs, he said he had long been frustrated that in a country with immense natural resources, tens of millions were living in poverty.

Once he began, one move led to another: He freed political prisoners, allowed open debate and multi-candidate elections, gave his countrymen freedom to travel, halted religious oppression, reduced nuclear arsenals, established closer ties with the West and did not resist the fall of Communist regimes in Eastern European satellite states.

But the forces he unleashed quickly escaped his control.

Long-suppressed ethnic tensions flared, sparking wars and unrest in trouble spots such as the southern Caucasus region. Strikes and labor unrest followed price increases and shortages of consumer goods.

Competitive elections also produced a new crop of populist politicians who challenged Gorbachev’s policies and authority.