Mr. Sanjuan, the son of a prominent composer and conductor, was fluent in nine languages (including Serbo-Croatian and Bulgarian), earned an advanced degree in Russian studies from Harvard and served in Navy intelligence.
In a federal career spanning two decades, Mr. Sanjuan described himself as a “rebel” and troublemaker who relished an argument and could be cutting in his demeanor. He served Democratic and Republican administrations through the 1970s and 1980s, holding mid-level posts at the Defense and Interior departments.
He retired in 1991 as director of the U.N. political affairs division, a job he later said amounted to spying on the Soviets who were spying on the Americans.
Mr. Sanjuan did Latino outreach for John F. Kennedy’s presidential bid in 1960. The next year, he joined the State Department as deputy chief of protocol under Angier Biddle Duke, the tobacco heir who became a mandarin of the diplomatic service.
Duke and Mr. Sanjuan used their office and political connections to help end the humiliations faced by non-white diplomats as they sought housing and restaurant service south of the Mason-Dixon Line.
Mr. Sanjuan was best known for efforts to persuade civic leaders as well as hotel and restaurant owners along U.S. 40 in Maryland to desegregate their facilities. In the years before Interstate 95 was completed, Route 40 was a main artery connecting Washington’s embassies and the United Nations.
The highway had long been a public embarrassment in its treatment of African Americans seeking food and shelter. High-level government involvement had been spurred by a series of embarrassing incidents involving African diplomats who were refused service.
Chad’s new ambassador to the United States, who was traveling to Washington in June 1961 to present his credentials to Kennedy, was snubbed by a cafe owner on Route 40 near Edgewood, Md.
“Our foreign policy in Africa was jeopardized for a measly dime — a transaction involving 10 cents,” Mr. Sanjuan told Maryland lawmakers in September 1961.
Over the next several years, the restaurants and hotels were targeted by protests from the Congress of Racial Equality, a civil rights group, and pressured by federal officials to change their discriminatory practices. Gradually, several restaurateurs agreed to change their policies.
Pedro Arroyo Sanjuan was born in Havana on Aug. 10, 1930. His father, also named Pedro Sanjuan, founded the now-defunct Havana Philharmonic Orchestra. His mother, Pilar Arroyo, was a professor and writer.
The family returned to Spain, but, by the end of the decade amid the civil war, they fled through the Basque country into France and eventually made their way to New York.
The younger Mr. Sanjuan became a U.S. citizen in 1947, graduated three years later from Wofford College in Spartanburg, S.C., and received a master’s degree from Harvard University in 1952.
In 1958, he married Patricia Martin. Her father, Edwin McCammon Martin, was a top Latin America expert at the State Department who served as ambassador to Argentina from 1964 to 1968.
Besides Mr. Sanjuan’s wife, of Somers, survivors include three daughters, Victoria Sanjuan of Peekskill, N.Y., Pilar Sanjuan of Albuquerque and India Sanjuan of Woodside, Calif.; and six grandchildren.
While at the Defense Department, Mr. Sanjuan participated in a task force that led President Gerald R. Ford to prohibit the Navy from using the inhabited Puerto Rican island of Culebra as a ship-to-shore gunnery range in 1975.
After a stint at the American Enterprise Institute, a public policy organization, Mr. Sanjuan became President Ronald Reagan’s assistant secretary of the interior for territorial and international affairs in 1981. Two years later, he left for the United Nations
He wrote a scathing book about his U.N. years, “The UN Gang: A Memoir of Incompetence, Corruption, Espionage, Anti-Semitism and Islamic Extremism at the UN Secretariat,” published by Doubleday in 2005.
The tone varied between sharp-tongued outrage and deadpan humor to make his points. Reviews were mixed, even in more-conservative publications such as the Wall Street Journal.
Mr. Sanjuan joked that he made it easy for those who did not wish to commit to buying the text. “In reading the title and subtitle, you don’t have to read the book actually,” he told the Washington Times.
In retirement, Mr. Sanjuan mostly focused on painting, sculpting and graphic arts, and he exhibited at the Corcoran and other galleries. His family said he was disinclined to name his pieces but caved, knowing titles would attract buyers.
He gave his paintings deliberately ludicrous titles, including “Coca-Cola Faerie Queen” and “Homage to Militarists.”