In 1956, Spreti became West Germany's first ambassador to Luxembourg since the Second World War, and held that post until 1960, when he became the ambassador to Cuba (until 1963), then to Jordan (1963–1965) and to the Dominican Republic (between 1966 and 1968). Finally he was dispatched to Guatemala during the turbulent times of the Guatemalan Civil War. On 31 March 1970 he was kidnapped by Marxist–Leninist FAR guerillas in Guatemala City and was murdered six days later. West Germany immediately severed diplomatic ties with Guatemala. Three days after Spreti's murder, an anti-communist death squad named Mano Blanca retaliated by assassinating the Communist politician César Montenegro Paniagua.