BOGOTA, Colombia (Reuters) -  The most important rebel commander ever captured by Colombia has been sent to the United States to face cocaine smuggling and kidnapping charges.

Colombia's president authorised the extradition on Friday of Ricardo Palmera, alias "Simon Trinidad", after the Revolutionary Armed Forces of Colombia, known by the Spanish initials FARC, failed to comply with an ultimatum to free 63 hostages including three Americans.

A federal court in Washington wants Palmera for alleged trafficking cocaine and involvement in kidnapping the FARC's American hostages.

Palmera, arrested in neighbouring Ecuador in January, was handed to U.S. officials at a Bogota military airport and escorted onto a U.S.-bound plane.

Wearing a bullet-proof vest, his hands cuffed behind his back, the bald-headed revolutionary was seen on Colombian television shouting as he was guided to the aircraft. It was not possible to hear what he was saying.

After arriving in Washington, Palmera appeared before Magistrate Judge John Facciola in U.S. District Court, the Justice Department announced.

He was named in two separate 2004 grand jury indictments for drug trafficking and giving terrorists material support and resources, the department said.

No FARC rebel of the rank of Palmera -- a 54-year-old former banker born into Colombian high society but radicalised by a murder campaign against leftists in the 1980s -- has been sent to the United States before.

President Alvaro Uribe has increased extraditions of suspected drug traffickers to the United States. Earlier this month he handed over former Cali cartel boss Gilberto Rodriguez Orejuela to U.S. agents.

But Uribe had offered to suspend Palmera's extradition if the FARC freed its hostages by Thursday this week.

PRESIDENT OFFERS REWARD

The FARC called the ultimatum blackmail and released no one, prompting Uribe to go on national television Friday evening from a southern jungle outpost where he was spending New Year's eve with army troops. He offered a $2 million (1 million pounds) reward to FARC members willing to turn in their commanders or tell the authorities where the kidnap victims are being held.

The FARC wants to swap its hostages -- who include soldiers, politicians and former presidential candidate Ingrid Betancourt -- for 500 imprisoned rebels.

The three Americans being held are U.S. government contractors captured by the 17,000-member rebel army in February 2003 when their aircraft crashed during a mission to find illegal drug crops.

Tough military action against the FARC -- which is fighting a 40-year-old war for socialist revolution that has claimed thousands of lives -- has given Uribe a public approval rating of about 70 percent as he plans to run for a second term in 2006.

The government regards extradition to the United States as its most fearsome punishment, partly because imprisonment there would put Palmera out of reach of amnesties granted in any future peace settlement.

Palmera, who has already been sentenced to decades in prison in Colombia for crimes including kidnapping, denies the U.S. charges against him. The FARC admits to "taxing" the cocaine trade and kidnapping for ransom.

"I am not a drug trafficker or a terrorist, and I will not only demonstrate that in the U.S. courts but will continue my political struggle," said Palmera, who insists on being called Simon Trinidad, in a recent jailhouse interview with the newspaper El Espectador.

He became a guerrilla 20 years ago and was one of the FARC's top negotiators during failed peace negotiations with the government of former President Andres Pastrana, a friend from his youth.

His extradition could backfire on the government, said Alfredo Rangel of the think tank Seguridad y Democracia, a former defence adviser to Uribe.