Robert O. Blake, a career Foreign Service officer and former U.S. ambassador to Mali who participated in Cold War diplomacy both in Moscow and in Washington, died Dec. 28 at his home in the District. He was 94.

He had metastatic prostate cancer, said his daughter, Lucy Blake.

Mr. Blake began his Foreign Service career in 1947, with his first overseas assignment in Nicaragua. Trained in Russian, and with expertise in Soviet affairs, he was posted to Moscow in the early 1950s — an assignment, he said in an oral history for the Association for Diplomatic Studies and Training, that was the "great adventure of all time."

As a consular officer, Mr. Blake recalled, he worked with three Russians “who, it was quite obvious, were reporting to the Soviet government — if, indeed, they weren’t members of the KGB.”

The most severe challenge he faced, he said, was the security of Americans with dual nationality.

“Most of them were children born in the United States of people who had come to the Soviet Union at the time of the Depression but had become very disillusioned with what was happening there,” he said in the oral history.

“Many of them had managed to slip out and get back to the United States. I don’t remember exactly how many of these people were left, but they were a sad bunch. One after another, the active ones were sent to prison camp in Siberia.”

After a stint in Tokyo, Mr. Blake returned to Washington, where he oversaw Soviet affairs at the State Department. Next came an assignment in Tunis, where he was a political officer during the retrenchment of French colonial influence in Africa.

He was assigned to the U.S. mission to the United Nations during the Cuban missile crisis of October 1962, then served as deputy chief of mission in Kinshasa, in what is now the Democratic Republic of Congo, and in Paris.

As ambassador to Mali from 1970 to 1973 — a “quiet but fascinating post,” he said — Mr. Blake worked on matters including famine relief. He later became deputy assistant secretary of state for international organizations before retiring from the Foreign Service in 1977.

Mr. Blake later worked in sustainable international development. He was a senior fellow in Washington for the International Institute for Environment and Development, a London-based policy research organization, and created the Committee on Agricultural Sustainability for Developing Countries, an independent nonprofit group based in Washington.

Robert Orris Blake was born in Los Angeles on April 7, 1921, and grew up in Whittier, Calif. He was a 1943 history graduate of Stanford University and, after Navy service in the Pacific during World War II, received a master’s degree from the School of Advanced International Studies at Johns Hopkins University in 1947.

He served on the boards of organizations including the Natural Resources Defense Council and volunteered with the Salvation Army and Meals on Wheels. His writings included an unpublished memoir, “Seeking the Heights: The Life and Times of Robert Orris Blake” (1996).

Mr. Blake had homes in Washington and in Somesville, Maine. Survivors include his wife of 59 years, the former Sylvia Whitehouse, of Washington; three children, Robert O. Blake Jr., the U.S. ambassador to Indonesia, of Jakarta, Lucy Blake of Palo Alto, Calif., and George Blake of Newport, R.I.; and five grandchildren.