By Juan Forero
Washington Post Foreign Service

BOGOTA, Colombia, May 7 -- Colombia on Wednesday for the first time extradited a senior commander of a right-wing paramilitary organization, sending him to the United States after he failed to cooperate with authorities investigating atrocities linked to death squads.

Wearing handcuffs and a bulletproof vest, Carlos Mario Jiménez, 42, was escorted onto a plane shortly after midnight and flown to Florida and then on to Washington, the Colombian president's office said in a statement. The paramilitary commander, once one of the South American nation's most feared men, faces charges of cocaine-trafficking and financing a terrorist group.

The government of President Álvaro Uribe, which has received $4.3 billion in mostly military and anti-drug aid from the United States since 2002, hailed the extradition. In a speech in Medellin, Uribe said it was a signal to other paramilitary commanders who fail to abide by an agreement that calls for them to confess to crimes in exchange for reduced sentences.

"We cannot give a prize to a person who goes back to committing crimes," Uribe said.

But some human rights and victims' rights organizations said the extradition effectively closes off the possibility of victims' families ever securing reparations from Jiménez or information about the slayings his forces committed in Colombia's shadowy conflict.

"The victims will unfortunately never have a chance to confront him, to question him directly and to get information to help them track down what happened to relatives who were massacred or disappeared," said José Miguel Vivanco, the Americas director of Human Rights Watch.

Prosecutors in Colombia consider Jiménez one of the three most brutal warlords to have formed the directorate of the United Self-Defense Forces of Colombia, a coalition of paramilitary groups. The AUC, as the group was known, was assembled to fight rebels but morphed into Colombia's top drug-trafficking cartel while carrying out massacres and illegally seizing land.

Jiménez was little known until the Uribe administration began negotiations with paramilitary commanders who wanted to disarm their fighters in exchange for leniency from the government. He commanded the powerful Central Bolivar Bloc, which ran a lucrative cocaine-smuggling operation while liquidating opponents and farmers, in part to erode support for rebels.

"He had 5,000 to 6,000 men and controlled several states," said Gustavo Duncan, author of a book on the paramilitary movement, "The Gentlemen of War." "He had great power and was a very important figure in Colombia."

Under a law governing the demobilization of paramilitary groups, commanders have to admit to their crimes and offer up their land and other possessions, which are to be turned over to the families of victims.

But most of the commanders have been less than forthcoming, leaving overwhelmed prosecutors unable to untangle thousands of cases.

Jiménez was seen by officials as among the least helpful. And though he was jailed, police determined that he continued to oversee a vast cocaine-smuggling network.

That prompted the Uribe government to seek his extradition. The move was blocked by a judge last month, but the judiciary's highest administrative panel overturned that decision Tuesday. The government then quickly hustled Jiménez onto a plane.

Iván Cepeda, who heads a group representing victims of paramilitary groups, filed a motion to stop the extradition, which he said could "signify impunity." Cepeda's organization has estimated that Jiménez's paramilitary bloc killed and disappeared as many as 10,000 people.

"This superimposes drug trafficking over crimes against humanity," he said.