BOGOTA, July 9, 2008 (AFP) - The United States on Wednesday transmitted a request to Colombia asking for the extradition of two FARC rebels seized in an operation last week that freed 15 hostages, Colombian officials said.

US authorities want to put the pair, Gerardo 'Cesar' Aguilar and Alexander 'Gafas' Farfan, on trial for abduction and terrorism, the foreign ministry officials said.

According to Colombian officials, the two were guarding the hostages who were freed when Colombian soldiers masquerading as aid workers flew in on a helicopter and took them all aboard.

The hostages included three US citizens -- Marc Gonsalves, Thomas Howes and Keith Stansell -- who were kidnapped by the Revolutionary Armed Forces of Colombia (FARC) in February 2003 while they were conducting an anti-narcotics mission in Colombia for the US military.

The United States considers the FARC a terrorist group.

The other hostages freed included Ingrid Betancourt, a Franco-Colombian politician, and Colombian soldiers.

A foreign ministry official said the US extradition request was being considered but did not say what the outcome would be. The US ambassador to Colombia, William Brownfield, on Tuesday had said the request would be lodged.

The lawyer for the captured rebels, Eduardo Matias, said the request should be opposed.

'The crime imputed to the two was committed on Colombian territory, so it should be Colombian courts that judge them,' he said.

The pair are being held in a high-security detention center in Bogota.

Neither made any comment when they paraded in front of the media after their capture. Both appeared to have been beaten.

Matias said his clients told him they had been surprised by the operation that freed the hostages, apparently rejecting accounts in the press suggesting that the rebels had been paid off to release their captives.

Aguilar, 49, is considered to be close to the military leader of the FARC, Jorge Briceno.

Farfan is seen as being the principal rebel in charge of keeping the hostages. Betancourt described him as 'almost sadistic' in his cruelty.

Apart from the charges being leveled against them by the United States, the two are also accused of drug trafficking in Colombia.