U.S. arms negotiator Max Kampelman speaks with President Reagan in the background before a gathering of congressmen on March 25, 1985, in Washington. (John McDonnell/THE WASHINGTON POST)

Max M. Kampelman, a longtime lawyer and political adviser who became a top Cold War diplomat, leading U.S. negotiations with the Soviet Union about the reduction of nuclear arms and the recognition of human rights, died Jan. 25 at his home in Washington. He was 92.

A son, Jeffrey Kampelman, said he had congestive heart failure.

Although not formally trained as a diplomat, Mr. Kampelman was skilled and patient in his dealings with Soviet officials in the 1980s, but he also managed to negotiate the treacherous political waters of Washington, gaining the trust of both Democrats and Republicans.

He was considered an elder statesman of official Washington, someone who never held political office but counseled many who did.

He began his career working for Sen. Hubert H. Humphrey (D-Minn.), who later was vice president under Lyndon B. Johnson and the Democratic nominee for president in 1968. By the 1980s, Mr. Kampelman was a key diplomat for Republican President Ronald Reagan.

In 1984, Mr. Kampelman was simultaneously a foreign policy adviser to Democratic presidential nominee Walter Mondale and a legal counsel to Edwin Meese III, who became Reagan’s attorney general in 1985.

During the 1980s, Mr. Kampelman led two prolonged series of international negotiations. The first, from 1981 to 1983, was officially known as the Madrid Conference on Security and Cooperation in Europe and helped bring about the release of political and religious dissidents from the Soviet Union.

The second set of negotiations, which began in Geneva in 1985, sought to limit the nuclear arms race between the United States and the Soviet Union. After years of talks, the two nations finally signed the first Strategic Arms Reduction Treaty, in 1991, a few months before the Soviet Union collapsed.

On Saturday, former secretary of state George P. Shultz praised Mr. Kampelman as “always steady, thoughtful and constructive.”

Mr. Kampelman was considered exceptionally patient and cordial in his dealings with the Soviets, but the negotiations were not without moments of stalemate and rancor.

“If you want to negotiate with the Soviets, you have to be prepared to stay one day longer than they,” Mr. Kampelman told The Washington Post in 1985. “If you are impatient to end it, you’re at a disadvantage.”

Too many diplomats made the mistake of trying to be “reasonable” with the Soviets, he said.

“Not that we should ever be unreasonable,” he told The Post. “But if you give at the start, you are losing out. This is important: Don’t look to show good will by making a concession, because it is interpreted not as good will but as a lack of will.”

Max M. Kampelman — he had only a middle initial, not a middle name — was born Nov. 7, 1920, in New York City. His parents were Jewish immigrants from Romania. His father was a butcher and later sold women’s hats.

Mr. Kampelman attended Jewish parochial schools before graduating from New York University in 1940. He then entered NYU’s law school at night while working for the International Ladies Garment Workers Union.

During World War II, as a registered conscientious objector, he participated in a wartime experiment at the University of Minnesota examining the effects of extreme weight loss.

While attending classes at the university, Mr. Kampelman’s weight fell from 160 pounds to 100. He and other participants in the study were later fed a variety of nutrients to gauge their recovery from starvation. The experiment was useful in treating prisoners of war and survivors of concentration camps at the end of World War II.

Mr. Kampelman received his law degree from NYU in 1945 and master’s and doctoral degrees in political science from the University of Minnesota in 1946 and 1951, respectively.

In 1946, Mr. Kampelman became an aide to Humphrey, who was then mayor of Minneapolis. After teaching briefly at Bennington College in Vermont, Mr. Kampelman came to Washington in 1949, when Humphrey entered the Senate. He was Humphrey’s legislative counsel until 1955, when he joined the Washington office of the law firm now known as Fried Frank.

He also renounced his earlier pacifist beliefs in 1955 and joined the Marine Corps as a reserve officer, serving until 1962.

As the head of his law firm’s D.C. office, Mr. Kampelman represented many high-profile companies and international figures, including Golda Meir, the onetime prime minister of Israel.

In 1968, Mr. Kampelman was a close adviser to Humphrey, who narrowly lost the presidential election to Richard M. Nixon. When the 1972 nomination went to George S. McGovern, Mr. Kampelman began to distance himself from the left-leaning elements of the Democratic Party.

In 1976, he was one of the leaders — along with Reagan and labor leader Lane Kirkland — of the Committee on the Present Danger, which recommended a tougher U.S. stance toward the Soviet Union.

In Washington, Mr. Kampelman was a founder of the D.C. National Bank, was active in Jewish philanthropic groups and was the founding president of the Friends of the National Zoo.

He was also chairman of WETA-TV and from 1967 to 1970 was the first moderator of WETA’s “Washington Week in Review.”

In 1967, Mr. Kampelman was nominated by President Johnson to be the first chairman of the newly formed D.C. Council, but he withdrew after a congressman accused him of being a “draft dodger” during World War II.

Mr. Kampelman received the Presidential Medal of Freedom from President Bill Clinton in 1999 and the Presidential Citizens Medal from Reagan in 1989. After the attacks of Sept. 11, 2001, he organized efforts to enact a worldwide ban on nuclear weapons.

His wife of 58 years, Marjorie Buetow Kampelman, died in 2007. Two of their children, David Kampelman and Anne Kampelman Wiederkehr, died in 2004 and 2006, respectively.

Survivors include three children, Jeffrey Kampelman of Chevy Chase, Julia Kampelman Stevenson of Washington and Sarah Kampelman of Hamilton, Va.; and five grandchildren.

Mr. Kampelman once noted that he had more than 400 hours of face-to-face meetings with Soviet negotiators, mostly over meals. In 1991, he held a meeting with diplomats, their families, interpreters and security staff members at the first McDonald’s restaurant to open in Moscow. He even hired a Russian band to play American music.

“It was a great success,” Mr. Kampelman wrote in the Chicago Journal of International Law in 2003. “Diplomacy is, after all, a human event involving human beings.”