Vadim V. Bakatin, a liberal Russian politician who in the late 1980s rocketed from Siberian obscurity to President Mikhail S. Gorbachev’s inner circle, then in the final days of the Soviet Union took control of the K.G.B. with a promise to curtail its size and strength — only to see it re-emerge under a new name soon after he stepped down — died on July 31 in Moscow. He was 84.

His death was announced by Russian state-owned news media, which did not specify the cause.

Mr. Bakatin assumed the chairmanship of the K.G.B., the feared Soviet spy agency, in August 1991, just days after a failed coup against Mr. Gorbachev. He did not want the job at first, but Mr. Gorbachev was short on options: Many of the people with experience running military or intelligence organizations had joined the effort to oust him, including the previous K.G.B. leader, Vladimir Kryuchkov.

Over the next few months, until his job vanished along with the Soviet Union itself, Mr. Bakatin undertook the herculean task of bringing the sprawling spy agency to heel.

He split off its armed divisions and its border guard unit, effectively cutting its personnel in half. He promised to end spying on politicians, journalists and foreign officials. He even fired his own son, a K.G.B. lieutenant colonel, as a signal that he would not tolerate nepotism or corruption.

He made several gestures of international good will. He allowed relatives of Oleg Gordievsky, a prominent defector, to join him in Britain after the Soviets had blocked them from emigrating for years.

He looked into allegations of Soviet involvement in the assassination of President John F. Kennedy (he found nothing, he said), and he gave the Swedish government several dozen documents related to the case of Raoul Wallenberg, a Swedish diplomat who disappeared at the end of World War II and was later reported to have been executed in Soviet custody.

He met with James A. Baker III, the United States secretary of state, and even gave Robert S. Strauss, the American ambassador, 70 pages of detailed schematics showing how the Soviets had bugged the U.S. Embassy in Moscow, along with a bag of the bugs themselves — a move that, even decades later, blemished Mr. Bakatin’s name among Russian nationalists.

He was much better liked by Western reporters, who often compared his disarming good looks to those of a news anchorman (he did bear a resemblance to the ABC newsman Peter Jennings). The novelist John le Carré interviewed him at length, as did the New York Times columnist William Safire.

Mr. le Carré came away impressed by Mr. Bakatin’s thoughtful transparency, Mr. Safire less so. “He is bamboozling the reformers and the Western press by using all the ringing words we like to hear,” Mr. Safire wrote.

Mr. Safire was on to something: Mr. Bakatin’s reforms fell short. He dissolved the K.G.B.’s board of directors but kept its members on the payroll. He promised to fire thousands of agents but let only a few dozen go.

He still believed in the Soviet Union, and he thought he could tame the security agency without having to kill it. But he also faced intense pressure from inside the government to keep the spy agency intact.

His counterpart in the Russian republic, Viktor Ivanenko, was a particularly dogged opponent, and when the Soviet Union disintegrated at the end of 1991 — and with it Mr. Bakatin’s job — Mr. Ivanenko effectively replaced him. He and his successors, including the future Russian president Vladimir V. Putin, rebuilt the agency, which is now known by its new Russian initials, F.S.B.

“It must be plainly said here that success was not achieved,” Mr. Bakatin told the Russian newspaper Izvestiya in 1992. “I do not believe that it was possible anyway to significantly reform anything in such a short time in the conditions that actually exist.”

“Thus,” he added, “I do not think that our special services have already become safe for our citizens. There are no laws, no control, no professional security services.”

Vadim Viktorovich Bakatin was born on Nov. 6, 1937, in Kiselyovsk, a small city in southern Siberia, about 2,300 miles east of Moscow. His father, Viktor, was a mine surveyor, and his mother, Nina (Kulikova) Bakatin, was a surgeon.

He graduated from the Novosibirsk Civil Engineering Institute in 1960. From 1961 to 1973, he worked as a foreman on large-scale construction projects around his hometown, a region rich in natural resources and busy with mining activity.

He joined the Communist Party in 1964 and nine years later went to work for the party full time. He rose steadily in the ranks, but by the early 1980s he seemed destined to remain a regional bureaucrat. He stood out, though, for his efforts to reform his corner of Soviet industry, pushing for decentralization from Moscow and limited economic liberalization.

His career took a sudden turn in 1986, when Mr. Gorbachev pulled him to Moscow to serve in the Communist Party’s Central Committee. Two years later, he was named interior minister.

“He was sure that I would never steal, and my weaknesses, my provincialism, were more to his advantage,” Mr. Bakatin told the Russian journalist Oleg Kashin in 2008. “Apparently, choosing me for this extremely important state post, he believed that I could be easily controlled.”

Mr. Bakatin brought his reformist agenda with him. He ended the use of paid informers by the Soviet police, introduced hot food for prisoners in pretrial detention and resisted efforts to use his ministry to suppress dissent.

Popular, handsome and well spoken, he quickly became a leading figure among Moscow reformers, and he was seen as a future prime minister or even a successor to Mr. Gorbachev.

But as the country began to crack at the turn of the decade, Mr. Gorbachev had to shore up his right wing. He fired Mr. Bakatin in December 1990 and replaced him with two hard-liners, Boris K. Pugo and Gen. Boris V. Gromov. Less than a year later, Mr. Pugo helped lead the failed coup attempt.

Mr. Gorbachev kept Mr. Bakatin close, naming him to his security council, a circle of top advisers. In 1991, Mr. Bakatin ran against Boris N. Yeltsin for the presidency of Russia, reportedly at the behest of Mr. Gorbachev, who saw Mr. Yeltsin as a rival. Mr. Bakatin came in last out of six candidates, with just 3.5 percent of the vote.

Still, he was a good enough politician that Mr. Yeltsin bore little grudge. He urged Mr. Gorbachev to make Mr. Bakatin head of the K.G.B. and later, after the Soviet Union collapsed, offered to make him an ambassador to any country he wanted, save France or the United States. Mr. Bakatin declined.

After leaving the government, Mr. Bakatin became vice president of Reforma, a civic organization, and an adviser to Baring Vostok Capital Partners, an investment firm.

His survivors include his sons, Alexander and Dmitri, and at least one grandchild.

Though his success at the K.G.B. was limited and short-lived, Mr. Bakatin made at least one discovery that may have made all his efforts personally worthwhile. Among the agency’s hoard of secret documents, he discovered that its predecessor, the N.K.V.D., had arrested, tried and executed his grandfather, a teacher, in 1937, just two months before Mr. Bakatin was born.

Milana Mazaeva contributed reporting.