Augusto Guillermo Arango, 71, a former Panamanian ambassador to the United States and then an official of the International Finance Corp., an affiliate of the World Bank, died Saturday at his home in Washington. He had cancer.

Mr. Arango became his country's ambassador here in 1960 and served until 1964, when he resigned. During the same period, he was ambassador to the Organization of American States and from 1962 to 1964 also was Panama's ambassador to Canada. He was chairman of the OAS fact-finding mission to the Dominican Republic in 1964.

As an official and consultant of the International Finance Corp., he was engaged in economic development projects in Central America and elsewhere in the world. After his retirement in about 1973, he was a private investment counselor.

Mr. Arango was born in Panama and educated in France and Switzerland, where his father was the Panamanian minister. He graduated from the Wharton School of Finance and Commerce, the University of Pennsylvania, in 1932. He then returned to Panama and was a businnesman and government servant. He represented Panama at several international economic conferences, including the Bretton Woods international monetary conference in 1944.

In 1964, Mr. Arango became a U.S. citizen.

His marriage to the former Pauline Sempier ended to divorce.

Survivors include his wife, Jacqueline, of Washington, a daughter, Paula Susan Arango of Roswell, N.M., and two sisters and a brother in California.