Updated

A prominent Colombian guerrilla will remain in prison in the United States, a U.S. official said Monday, dismissing rebel appeals for the man to be freed for peace talks in Cuba.

The Revolutionary Armed Forces of Colombia, or FARC, recently appealed to President Barack Obama to release Ricardo Palmera, who is better known by the nom de guerre Simon Trinidad.

Ricardo Zuniga, a special assistant to Obama and the lead official for Latin America policy on the National Security Council, noted that the U.S. government isn't part of the negotiations in Havana.

"This person is in prison for very serious crimes and is going to remain imprisoned," Zuniga told The Associated Press in a phone interview. He first made similar remarks to the Colombian newspaper El Tiempo an interview published Monday.

Zuniga declined to discuss whether the U.S. government would be willing to consider changing its posture under certain circumstances.

The FARC had said the rebel's presence at the talks with the Colombian government in Havana would help the negotiations.

The rebels named Palmera to their negotiating team in September, even though the 62-year-old is held at a maximum-security prison in Florence, Colorado. The rebels recently brought a life-sized cardboard cutout of him to a negotiating session.

But American officials have previously said it's unlikely any FARC rebels imprisoned in the US would be freed.

Palmera was captured in 2004 while trying to negotiate freedom for imprisoned rebels in exchange for three American contractors held hostage in jungle gulags by the FARC. The Americans were rescued four years later, along with former Colombian presidential candidate Ingrid Betancourt.

Palmera was extradited to the U.S., then a jury in Washington convicted him and he was sentenced to the maximum of 60 years in prison for hostage-taking conspiracy.

The formal peace talks in Havana began last week. On Sunday, the Colombian government and the leftist rebels announced that as part their dialogue they will hold a forum in Bogota in December to discuss agrarian development, which has been an issue in the class-based conflict.

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Associated Press writer Luis Alonso Lugo in Washington contributed to this report.