A former guerrilla leader wanted in the United States on drug-trafficking charges was sworn-in Tuesday as a member of the Colombian Congress.

Jesus Santrich took the oath of office at 8.00 am in a private ceremony presided over by Atilano Giraldo, a member of the leadership of the House of Representatives.

"I must go first to the Supreme Court of Justice to respond to and comply with the requirements of that judicial authority," the new congressman told reporters when asked if he would be taking part in Tuesday's legislative session.

The court is weighing the evidence in support US request for extradition of Santrich, 52, who was a commander in the now-demobilized Revolutionary Armed Forces of Colombia (FARC).

He spent a total of 416 days behind bars before a May 30 Supreme Court ruling that Santrich was entitled to certain protections because a seat in Congress had been reserved for him under the terms of the government's 2016 peace deal with the FARC.

Colombia is one of a number of Latin American countries where a criminal case against a legislator or senior official can be brought only with approval from the highest court.

The peace accord set aside 10 seats in Congress - five each in the Senate and House - for people to be designated by the political party of the former insurgents, the Common Alternative Revolutionary Force, also known by the acronym FARC.

Santrich, who helped negotiate the agreement that ended five decades of conflict in Colombia, was unable to take his seat as originally scheduled, on July 20, 2018, because he had been arrested three months earlier on an Interpol Red Notice issued at Washington's request.

US prosecutors accuse him of having conspired to ship 10 tons of cocaine to the United States after the signing of the 2016 peace pact, putting the alleged offense beyond the scope of the transitional justice system Bogota created in conjunction with the peace process.

Santrich has pledged to cooperate fully with the Supreme Court as he seeks to clear himself.

Colombia's rightist president, Ivan Duque, said Monday during a visit to Argentina that Santrich is a "mafioso" who will be found guilty of drug trafficking.

Santrich reacted to those comments by urging Duque to "act as the president of everyone, giving guarantees, and also to take into account that there is something called the presumption of innocence." EFE