Samuel D. Berger, 68, a former U.S. ambassador in South Korea and deputy ambassador to South Vietnam, died of cancer Tuesday at his home in Washington.

A career Foreign Service officer, Mr. Berger served in Seoul from 1961 to 1963 and in South Vietnam from 1968 to 1972, when the U.S. presence there reached its peak even while efforts were begun to end the war there.

In an interview shortly before his death, Mr. Berger said that by the time he arrived in Vietnam in March 1968, the Tet offensive by the Communist forces, although defeated had broken the American will to achieve a military victory.

"Our policy became one of buying as much time as we could," he said. "We tried to win the war with money and people instead of brains."

Mr. Berger said that while the United States built up its own forces it failed to provide sufficient material support for the Saigon government. In turn, he said, the Saigon government, although it had made progress militarily and in such areas as land reform, failed because of the narrow base of its leadership.

As ambassador to Korea, Mr. Berger became known to the press as "Silent Sam" because of his penchant for withholding comment. It was during those years that he tried to implement the United States policy of getting Chung Hee Park to hold elections.

"You work with what you have," Mr. berger said in his recent interview. "Sure, it would have been wonderful to have had a democracy in Korea at that time, but the government that existed made gigantic strides in economic growth."

It was in Korea that Mr. Berger gained a reputation as a tough administrator as well as an able diplomat. "I did not have a philosophy; I don't know or care if these people were Republicans or Democrats," he said. "I gave them a job. If they couldn't do it, I got rid of them."

Mr. Berger also said that he learned to work with Gen. Park whom he described as being open to suggestions for economic and labor reforms.

Many of Mr. Berger's career assignments were in Pacific nations. In addition to Korea and Vietnam, he had been political counselor in Tokyo and deputy chief of mission in New Zealand. But he had begun his Foreign Service career as a labor specialist in Europe, where he served in Great Britain and Greece.

Mr. Berger was born in Gloversville, N.Y., and was a graduate of the University of Wisconsin where he studied labor economics and history. He went to Britain in the late 1930s on a Carnegie fellowship to study the British trade union movement.

He began his government service in 1940, and two years later joined the Lend-Lease Mission to Great Britain to work on manpower and labor problems. He later worked on problems such as coal production and shipping, which brought him into contact with British labor officials.

Mr. Berger was particularly valuable to the U.S. Embassy after the Labor Party came to power in 1945.

From 1953 to 1954, Mr. Berger was political counselor at the U.S. Embassy in Tokyo. He ran afoul of then vice president Richard M. Nixon during this period by maintaining that the Communist Party presented no threat to the internal stability of Japan. As a result of this dispute, he was assigned to embassies in New Zealand and Greece for the next seven years.

He was nominated ambassador to South Korea in 1961 by president John F. Kennedy. He later was deputy assistant secretary of state for East Asian affairs. At the time of his retirement in 1974, he was an official of the Foreign Service Institute.

His first wife, the former Margaret Fowler, died in 1966.

He is survived by his second wife, Elizabeth Lee Berger of Washington; three stepdaughters, Jean Patitucci of Palo Alto, Calif., Margaret Wooding of London England, and Sheridan Pressey of Washington; two brothers, Graenum, of Pelham, N.Y., and Milton, of Gloversville; a sister, Sadie Finn of Portland Ore.. and two step-grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the DACOR Education ad Welfare Fund, 1718 H. St. NW. c