BY GLENN GARVIN AND CATALINA CALDERON

 SAN JOSE, Costa Rica -- A conference billed as a chance for the combatants in
 Colombia's civil war to spend a few days slinging words instead of bullets fizzled
 into irrelevance Tuesday with word that the country's most powerful Marxist
 guerrilla group would not attend.

 With right-wing paramilitary groups already absent -- the humanitarian groups that
 organized the conference refused to invite them -- the decision by the Rebel
 Armed Forces of Colombia, or FARC, to skip the talks meant little could come of
 them.

 FARC officials apparently decided they did not want to share the stage with a
 smaller guerrilla group, the National Liberation Army, or ELN, which is attending.

 A FARC spokesman said the talks in San Jose would undermine formal peace
 negotiations between FARC and President Andrés Pastrana's government -- talks
 in which the ELN plays no role.

 ``We think this is a way to play to the gringos and to Pastrana now that they don't
 want to continue with the peace process but instead pursue Plan Colombia,'' said
 FARC spokeswoman Olga Marín.

 Plan Colombia is a scheme, backed with $1.3 million in aid from Washington, to
 use troop deployments and aerial spraying of herbicides to eradicate heroin and
 cocaine production, eliminating the guerrillas' principal source of funds.

 Organizers of the Costa Rica conference spent several hours debating whether to
 cancel it after receiving word late Monday night that FARC's delegation would not
 show.

 They decided to continue, and even offered a 100-day cease-fire plan that would
 kick off Dec. 1. But they agreed that without the consent of either the FARC or
 the right-wing paramilitaries, it was not clear how much fire would really cease.

 ``To achieve peace, we need the participation of all parties,'' said Anders
 Kompass of the United Nations High Commission for Human Rights.