STOCKHOLM, Sweden (AP) -- Sten Andersson, a leading figure in Sweden's governing Social Democratic Party and one-time mediator in the Middle East peace process, has died, the party said Saturday. He was 83.

Andersson, who had retired from politics, died Saturday on the eve of national elections, party spokesman Manuel Ferrer said. He did not disclose the cause of death.

Born in 1923, Andersson worked his way up the Social Democratic ranks in the 1950s. He served as party secretary for 20 years and was appointed social affairs minister in 1982 in the government of Olof Palme, who was assassinated in 1986.

As foreign minister from 1985 to 1991, Andersson helped start a dialogue between the Palestine Liberation Organization and the United States. He developed close relations with late Palestinian leader Yasser Arafat and remained involved in the Middle East peace process in the 1990s. "He was a committed debater, filled with joy and a sense of humor, a fantastic organizer and internationalist," Prime Minister Goran Persson said in a statement

Information on survivors and funeral arrangements was not immediately available late Saturday. The Social Democrats planned a memorial service Sunday at party headquarters in Stockholm.