BOGOTA, Colombia — U.S. prosecutors have apparently won the cooperation of a key witness in the case of a top rebel ideologue arrested last week on charges of trying to import 10 metric tons of cocaine into the U.S.

An official from Colombia's chief prosecutor's office said Marlon Marin was flown Monday to New York after agreeing to testify against co-defendant Seuxis Hernandez, better known by his alias Jesus Santrich. The official spoke on condition of anonymity because he wasn't authorized to discuss the politically charged case, which has upended the already stumbling peace process with the Revolutionary Armed Forces of Colombia.

Marin is the nephew of Luciano Marin, better known as alias Ivan Marquez, who with Santrich's help led the FARC in peace talks that concluded in 2016 with an agreement to end a half century of fighting.

Both were arrested in Colombia last week on U.S. charges. Audio recordings secretly obtained by U.S. investigators and released by Colombia's chief prosecutor last week purportedly showed Marin arranging meeting between members of the Mexico-based Sinaloa Cartel and Santrich. In one of the recordings Marin is also heard allegedly negotiating the payment of a large cocaine shipment with an alleged Mexican cartel member.

Authorities also seized from a Bogota apartment a drawing Santrich allegedly made for Rafael Caro Quintero, one of Mexico's most-notorious narcos, who last week was added to the FBI's 10 most-wanted list of fugitives. The drawing is dedicated to "Don Rafa Caro" from Santrich "with hopes of peace."

Prosecutors for the southern district of New York did not return emails seeking comment.

The FARC has strongly defended Santrich, accusing Colombian and U.S. authorities of laying a trap to sabotage the peace deal. But the ex-rebels also made clear that the embarrassing arrest would not reverse their decision to turn over their weapons and form a political movement. Santrich was one of 10 former rebels set to take up seats in congress guaranteed the FARC as a result of the peace deal.

Santrich, who says he is on a hunger strike from jail, said that he would rather die of starvation than be extradited. In an interview Tuesday with Colombia's W Radio, the blind former rebel ideologue confirmed that he had conversations with Mexicans over the phone, but thought at the time that they were businessmen interested in investing in post-conflict projects in Colombia.

"It's more likely that cocaine passed through the nose of the chief prosecutor of the nation than through my hands," he said.

Under terms of the peace accord, rebels who lay down their weapons and confess their war crimes are to be spared jail time and extradition. But they aren't protected for crimes committed after the December 2016 signing.

A special tribunal set up by the accord will rule on whether Santrich's alleged past crimes are covered by the agreement in what experts say is a major test for the peace process' credibility.

Marlon Marin, in his Facebook page, can be seen posing in aviator-style sunglasses and polyester suits next to yachts and vintage cars, and is seen vacationing in the Colombian city of Cartagena as well as Havana, where peace talks between the FARC and government took place. Friends jokingly nicknamed him "patron," Spanish for the boss.

Though the 39-year-old was not a member of the FARC, the official said Marin was close to the group's leadership and often showed up at their meetings. He had no previous criminal record, but had been the target of an investigation by Colombian authorities for allegedly taking bribes from businessmen to secure contracts for post-conflict projects managed by the FARC and the Colombian government.

When asked in a press conference about his relationship with his nephew, Marquez only referred to him as a "gentleman" whose "conduct will have to be investigated."

He then changed the topic back to Santrich, the supposed ringleader of the group trying to export cocaine to the U.S.

"How can they blame a blind man for organizing cocaine shipments?" Marquez said.