Luis Machado, 79, a retired World Bank director who was Cuba's ambassador to the United States from 1950 to 1952, died Monday at Suburban Hospital in Bethesda following a heart attack.

He was an executive director of the World Bank from 1946 to 1948, and again from 1954 to 1970. Following his retirement, he served as a consultant to a number of organizations, including the International Finance Corporation and the Honduran Embassy.

Dr. Machado came to Washington as ambassador in 1950 with the credentials of a lawyer, businessman, and economist. Although he had represented Cuba at a number of international conferences and held several government posts, he was neither a politician nor a career diplomat.

During his years as ambassador, he gained a reputation as a forceful representative of his country's views and an eloquent proponent of economic cooperation with the United States.

He also was known as a diplomat who could get results. He once surprised Pentagon officials, who were prepared for weeks of negotiation, by reaching an agreement on sugar purchases in less than an hour. He simply called the president of Cuba on the telephone from the Cuban Embassy and cut through the red tape.

Although asked to remain as ambassador, Dr. Machado resigned after Batista became ruler of Cuba. He remained in exile after Fidel Castro came to power.

He received a number of awards and decorations from various Latin American countries, beginning with the award of commander in Chile's Order of Merit in 1938, to Panama's Order of Balboa in 1963.

After receiving Guatemala's Grand Cross of the Order of Quetzal in November 1963, he was called upon to make a speech.

Dr. Machado's response was to say that he was reminded of a couple of Spanish proverbs. "The less you deserve an honor," he said, "the more you should appreciate it." He then noted that in Spain they say, "'If you want to find your real friends look in the cemetery, the hospital or the jail,' but I add -- or in exile."

Although his life ended in exile, he began serving his country in 1919 as secretary to the Cuban delegation to the Versailles Peace Conference. He later represented Cuba at the Bretton Woods Conference in 1944, which led to the founding of the International Monetary Fund and the International Bank for Reconstruction and Development (World Bank).

Dr. Machado was born in Guanabacoa, Cuba. He earned a bachelor's degree at Havana Institute and a degree in civil law and a doctorate in international law at the University of Havana.

During the 1940s, he was a delegate to international conferences on radio and communications and civil aviation and was elected president of the United Nations Economic Conference on Latin America in 1949.

Dr. Machado was a practicing lawyer in Havana for a number of years. He belonged to the Cuban Institute of International Law and was a member of the governing board of the Havana Bar Association in 1936.

Survivors include his wife, Genoveva, of the home in Bethesda; three daughters, Irene Castellanos, of New York City, Elena Lowenfeld, of Riverdale, N.Y., and Natalia de Maruri, of Bilboa, Spain; a brother, Roberto, of Washington, a sister, Maria Teresa Poey, of Miami, Fla.; eight grandchildren and one great-grandchild.