James Histed Lewis, 87, a Foreign Service officer who retired in 1973 after serving as deputy chief of mission and acting ambassador to Finland, died of pneumonia and congestive heart failure Dec. 9 at Suburban Hospital. He lived in Chevy Chase.

Mr. Lewis was a native of Carbondale, Pa., and a graduate of George Washington University, where he also received a master's degree in international law.

He began with the State Department in 1936 as a staff officer in the trade agreements division. He was named special assistant to the ambassador to Britain in 1942 and later was an economist and staff aide in Washington and a member of the delegation to the Paris peace conference after World War II.

Other postwar assignments were chief of the British branch of State's commercial policy division and delegate to the General Agreement on Tariffs and Trade. He was head negotiator at three GATT conferences between 1950 and 1961.

In the 1950s, Mr. Lewis was also first secretary and consul in London and economic affairs counselor in Copenhagen. He was named chief of the trade agreementsdivision in Washington in 1961 and then was chief of commercial policy and treaties and deputy director of the office of international trade.

In the 1960s, he was minister-counselor for economic affairs at the U.S. mission in Geneva and deputy director-general of the GATT secretariat at the United Nations.

Mr. Lewis was an elder and president of the trustees of Georgetown Presbyterian Church and had served as lay minister of the Anglican Church in Helsinki.

Survivors include his wife of 56 years, Betty Lewis of Chevy Chase; four children; a brother, Nobel Prize-winning geneticist Edward B. Lewis of California; and four grandchildren.