David K. E. Bruce, who had the unique distinction of having served as the top American diplomat in France, West Germany, Britain and China, died yesterday of a heart attack. He was 79.

A Georgetown University Hospital spokesman said that the veteran diplomat died at 2:10 a.m. He had been admitted to the intensive care unit at 10 p.m. Sunday. Although Dr. Richard Perry said that Bruce had suffered from irregular hearbeat for the last nine years and had been taking medication, he had been active until he became ill at dinner time on Sunday.

W. Averell Harriman, a close friend, called Bruce "the most brilliant representative of our country abroad in my generation. He had the unique ability to understand the problems of the other countries he dealt with and at the same time to have the clearest grasp of our own concerns."

Joseph Alsop, the journalist who knew him well, called Bruce "one of the greatest public servants America has had." He had served under every President from Truman to Ford.

Bruce's career was an extraordinary one by any measure. A tall, handsome, impeccably attired man whose hair had turned silver, he was famour for his unflappability and his dry wit. Perhaps his greatest achievement was the role he played in the post-World War II years when he was variously described as an "apostle" or "a zealot" in the European unity movement, a close ally of France's Jean Monnet.

His ambassadorships to Paris and Bonn had much to do with ending the ancient Franco-German battles and creating the first successful efforts to bring Western Europe together.

To Bruce, diplomacy was "not a system of moral philosophy" but rather "the application of intelligence and tact to the conduct of official relations between the governments of independent states."

Within that framework, Bruce felt than an ambassador should be able to influence decisions of his government without himself being a policy maker. That, indeed, was the role he played in American diplomacy.

David Kirkpatrick Este Bruce was born in Baltimore on Feb. 12, 1898. His father, William Cabell Bruce, was a Democratic Senator from Maryland and his mother, the former Louise Este Fisher, belonged to one of the state's leading families. He enrolled in Princeton in 1915 but left to join the Army at 19 during World War I. After the armistice he studied law at the University of Maryland and the university of Virginia, then began to practice in Baltimore.

Bruce's 1926 marriage to Ailsa Mellon, only daughter of the then Republican Secretary of the Treasury Andrew W. Mellon, was the social event of the year in Washington. Congress adjourned early so members could attend. Bruce helped Mellon with preparations for creating what is now the National Gallery of Art, of which he served as the president. The marriage ended in divorce in 1945. There was one daughter, the late Mrs. Stephen Currier.

Bruce's second marriage was to Evangeline Bell, daughter of a foreign service officer. They had three children, Alexandra, whose 1975 death was ruled a suicide, and two sons, David and Nicholas. The Bruce home is in Georgetown.

In the 1920s, Bruce had a hand in various business interests. He also was elected as a delegate to the Maryland legislature. After spending two years in the foreign service, serving as a vice consul in Rome, he worked in New York, including a while with Averell Harriman's international banking firm. He then established residence in Virginia and in 1939 was elected to the Virginia House of Delegates. He was always amused when political people discovered that this diplomat had served in two state legislatures.

In 1939, he wrote his only book, "Revolution to Reconstruction," a history of the first 16 presidencies. Normally, he was taciturn about his diplomatic activities unless he wanted to influence the press on some on-going government policy. Then his personal charm, coupled with a distinguished intellect, could work wonders.

In June, 1933, on behalf of Harriman's sister, Harriman himself and others. Bruce was a bidder at the bankruptcy sale of The Washington Post. He said only last week that he had been piced for that task because he was unknown in Washington. The paper was sold, instead, to Eugene Meyer. After The Post purchased the Times-Herald in 1954, publisher Philip L. Graham, a great admirer of Bruce, proposed that the diplomat join in ownership and control of the paper, but the flattered Bruce declined.

When World War II began in Europe, Bruce headed the American Red Cross mission in London. In 1941, he helped organize the Office of Strategic Services, the forerunner of the Central Intelligence Agenc Bruce was OSS chief in Europe from 1943 to 1945, with the rank of colonel.

He went ashore in Normandy with OSS Chief came under "Wild Bill" Donovan. When they came under fire, Donovan said they must not be captured and asked if Bruce had his instantaneous death pill. Bruce didn't, and neither did Donovan. The OSS chief then said not to worry, "if we are about to be captured, I'll shoot you first. After all, I am your commanding officer."

With Ernest Hemingway, Bruce entered Paris on liberation day. His love affair with France, and the French, never ended.

At war's end, when Harriman was named Secretary of Commerce, he picked Bruce as an assistant secretary. When Harriman was sent to Europe by Truman to head the Marshall Plan, Bruce went to head the plan for France. Alfred Friendly, who worked for Harriman during leave from The Post, of which he later was managing editor, recalled Bruce's performance as "magnificent." He also remembered that Bruce had "one of the finest wine palates in the world," of which he was proud. By now Bruce also was an art collector.

In 1948, Bruce was named ambassador to France.Dean Acheson, long his boss, wrote that "it is no exaggeration to say that not since Benjamin Franklin had anyone been closer to or more understanding of the French situation." Bruce spoke impeccable French, recalled former diplomat Lucius Battle, who worked with him in those years.

France then faced enormous problems and the ambassador, with no public fanfare, played an enormous role in its internal affairs, helping to institute austerity programs, cut inflation and otherwise get the nation back on its feet. He came home from Paris to be Undersecretary of State in 1952, but administration was not much to his liking.

The next year he was back in France trying to bring the Western European nations together in the European army scheme, EDC. Bruce tried hard, but the French finally scuttled the idea. He was more successful in his close working irelationship with Jean Monnet in the establishment of the European Coal and Steel Community, the first step toward unity.

President Eisenhower named Bruced ambassador to Germany in 1957, despite some Republican protests over Bruce's contributions to his own Democratic party. Bruce was a wealthy man, always a Democrat but never a partisan, seving both parties faithfully and fully.

In Bonn, Bruce concentrated on establishing a close relationship with Chancellor Konrad Adenauer. Once again the diplomat was influential in reducing Franco-German antagonisms.

Journalist David Schoenbrun wrote that Bruce was less popular in Germany than in France, "perhaps because he was tempermentally less attracted to the Germans and the German way of life." But no one could tell that from his conduct.

Bruce left Bonn before the 1960 presidential election, serving as a Democratic foreign policy adviser. he also spoke for the Virginia Committee on Religious Freedom against religious prejudice toward the candidacy of John F. Kennedy.

If Bruce had been younger - he then was nearing 63 - Kennedy quite probably would have named him Secretary of State. Instead, he sent Bruce to London as the ambassador. Walter Lippmann called it "pre-eminent among the notably good appointments." He was immensely popular with the British and President Johnson kept him in London until he retired in 1969 after a stay longer than that of any predecessor.

President Nixon picked Bruce in 1970 as "superbly qualified" to represent the United States at the Paris peace talks on the Vietnam war. But Bruce had no real negotiating room, the job came to naught and he retired after 16 months.

In 1973, when Bruce was 75, Nixon named him the first American head of the newly established liaison office in Peking, with the rank of ambassador but short of the formal title. The appointment was a complement to the Chinese who respected Bruce both for his age and for his rank as a senior diplomat. There was not much to do, however, because Peking and Washington could not agree to proceed further in their diplomatic relationships. So Bruce again retired.

Finally, in 1974, President Ford named Bruce as the ambassador to the North Atlantic Treaty Organization in Brussels. He served at NATO for 16 months, retiring from the diplomatic corps in February, 1976, at the age of 78. On his retirement, Ford presented Bruce with the Medal of Freedom. Bruce settled in his Washington home with his wife who had served as his well-liked hostess in so many posts.

When Bruce left London he declared that "the cardinal rule for an ambassador in a foreign country is to cherish no antipathies or attachments for domestic political parties or programs. This does not forbid him to contract friendships regardless of parties, or love the country of his residence dispassinately."

The State Department yesterday expressed regret at Bruce's death, calling him "among the most eminent diplomats of his generation." As Averell Harriman added: =He never tired but was always ready to take on new and difficult assignments."