Ferdinand Kuhn, 73, a noted writer on international affairs and a former newspaperman, died at Washington Hospital Center Tuesday following a heart attack.

Mr. Kuhn was the first full-time diplomatic correspondent of The Washington Post. He joined the newspaper in 1946 and stayed until 1953. The Post was not a profitable enterprise in those years, and Mr. Kuhn once remarked that it "will cover any international conference there is, as long as it is in the first taxi zone."

Budgetary restrictions notwithstanding, Mr. Kuhn made several trips aboard for The Post. He visited Moscow in 1947, the Ruhr and Berlin in 1948, Greece, Turkey and Iran in 1951, and Japan in 1952.

In 1953, he and his wife, Delia, embarked on careers as freelance writers on world affairs. They traveled frequently in Europe, North Africa and Asia and produced numerous magazine articles and newspaper series and several books. They visited China last summer.

Mr. Kuhn was born in New York City, graduated from Columbia University with honors in 1925, and became a reporter on The New York Times. He was assigned to its London bureau in 1928 and became chief London correspondent in 1936. He returned to the United States in 1939.

After a brief stint as an editorial writer for The Times, he moved to Washington where he was an assistant to Treasury Secretary Henry Morgenthau from 1940 to 1943. He then became deputy director of the Office of War Information and chief of its British division.

He joined The Washington Post after a year as head of the international information service of the State Department.

Colleagues recalled Mr. Kuhn as a reporter who would cover great events and still maintain an interest in the lives of ordinary people.

Chalmers M. Roberts, who succeeded Mr. Kuhn as diplomatic reporter for The Post, said Mr. Kuhn's "years with the (newspaper) were terribly important to (its) history in raising its standards of diplomatic reporting from the mediocrity of the past to create the foundation on which is modern diplomatic reporting is based. He was one of those marvelously educated men who understood the realities of world affairs without being cynical about them."

Alan Barth, a former editorial writer for The Post, said Mr. Kuhn's conception of his role as a foreign correspondent was to give his readers "an insight into the ordinary lives of the people he was covering."

James Reston, whom Mr. Kuhn hired for The New York Times, described his former boss as a "really serious journalist." He added that "the imponderable" about Mr. Kuhn was his "gift of kindness. If anybody ever was in trouble, he was the guy who showed up."

Mr. Kuhn wrote two books for children, "Commodore Perry and the Opening of Japan" (1955) and "The Story of the Secret Service" (1957). With his wife he wrote three other books - "Borderlands" (1962), "Russia On Our Minds, Reflections on Another World" (1970) and "The Philippines Yesterday and Today" (1966).

His honors included the French Legion of Honor, the Sigma Delta Chi award for best foreign correspondence in 1951 and the Columbia University medal for distinguished service in 1939.

In addition to his wife, of the home in Washington, survivors include two sons, Philip Alden, a professor of Chinese history at Harvard University, and David Antony, a poet and farmer who lives in Jailly-Les-Moulins, Burgundy, France, and one grandson.