Fumihiko Togo, 69, a Japanese career diplomat who served as ambassador to the United States during the Ford and Carter administrations, died of intestinal cancer tonight in a Tokyo hospital.

Mr. Togo was deeply involved in U.S. -- Japan relations for much of his career. He played an important role in negotiations to renew the Japan-U.S. security treaty in 1960 and was chief negotiator in 1969 at talks with the United States on returning Okinawa to Japanese control.

He served as ambassador in Washington from 1976 to 1980, a period in which Japan and the United States moved closer in economic relations although there were disputes centering on steel, television sets and farm products.

Toward the end of Mr. Togo's tenure in Washington, U.S. embassy personnel were taken hostage in Iran. According to his family, Mr. Togo told Tokyo strongly that it should not underestimate the strength of American emotions on this issue. But Japan declined to stop all oil imports from Iran, as the United States had requested, resulting in tension with Washington.

Mr. Togo was born Fumihiko Honjo in Tokyo in 1915, the fifth son of a banker. He graduated from Tokyo Imperial University in 1939 and immediately entered the diplomatic service. He was studying at Harvard University when the attack on Pearl Harbor occurred on Dec. 7, 1941, was interned and later sent back to Japan.

Mr. Togo served in the Foreign Ministry during World War II and in 1943 married Ise Togo. She was the daughter of Shigenori Togo, another career diplomat and the foreign minister of Japan from 1941 to 1942 and again in 1945.

Shigenori Togo formally adopted his son-in-law and conferred on him his surname, a common practice in Japan when families have no male heir.

In 1958, Mr. Togo became director of the Foreign Ministry's security bureau. In 1967, after serving as consul general in Calcutta and New York, he was named director general of the ministry's North America division.

From 1970 to 1972, he was Japan's ambassador to South Vietnam. Later he became vice minister, the ministry's top job for a career official. He retired in 1980, but remained active as an adviser to the ministry and to Nippon Steel.

Survivors include his wife, Ise, and two sons, Shigehiko and Kazuhiko.