Colombia's largest rebel group is seeking support from an unusual source in its effort to negotiate an exchange of imprisoned guerrillas for hostages: Hollywood actor Denzel Washington and directors Oliver Stone and Michael Moore.

The three celebrities were addressed in a letter from the Revolutionary Armed Forces of Colombia — also known as FARC — asking for help in pressuring their government to release 600 imprisoned rebels in exchange for 62 hostages, including three U.S. defence contractors captured in 2003.

Also asked to advocate for the swap were leftist academics Noam Chomsky, James Petras and Angela Davis, and activist Jesse Jackson.

"To the people of the United States, we ask for your always generous solidarity to pressure President Bush and his government to support a prisoner exchange in Colombia," said Raul Reyes, the chief spokesman forFARC.

Both directors have made political films in the past which might explain their inclusion on the list: Stone with Salvador and Moore with Fahrenheit 9/11. Likewise Chomsky was recently promoted by Venezuelan President Hugo Chavez at a recent meeting of the United Nations.

The inclusion of Washington, one of Hollywood's most prominent actors, is puzzling, though in his last movie role he played a police detective attempting to negotiate with a bank robber in director Spike Lee's The Inside Man and he has played activists such as South Africa's Steve Biko and U.S. leader Malcolm X infilms.

FARC is holding three U.S. defence contractors — Thomas Howes, Keith Stansell and Marc Gonsalves — whose small aircraft went down in 2003 while intelligence gathering. Also among the hostages is former Colombian presidential candidate Ingrid Betancourt.

"Howes, Stansell and Gonsalves are alive in our custody, treated with respect and dignity in the jungle," said Reyes, who promised to send evidence the three were alive.

Colombian President Alvaro Uribe broke off negotiations with the group after claiming it was responsible for a car-bomb that injured 20 people. The government said it intended to use military operations to free the hostages but later relented after pressure from family members of the hostages.

Among the rebels the group wants released is Ricardo Palmera, also known as Simon Trinidad, who was captured in 2004 and stands trial in Washington, D.C., for the kidnapping of the three Americans.