Prosecutors for the US Department of Justice on Tuesday asked New York Judge Carol Amon to release Salvador Cienfuegos from prison so that Mexico can do its own probe and potentially prosecute him.

Amon said she had "no reason to doubt the government's determination that the Mexican prosecuting authorities sincerely wish to pursue an investigation and possible prosecution of this defendant."

During the brief hearing, she asked the 72-year-old Cienfuegos whether he accepted the agreement that he be escorted by US marshals to Mexico, where he currently faces no charges.

"Yes, I agree," he replied in Spanish.

US authorities arrested Cienfuegos at a Los Angeles airport in December to the surprise and irritation of Mexican officials.

The retired general was accused of conspiring to produce and distribute "thousands of kilograms" of cocaine, heroin, methamphetamine and marijuana in the US between December 2015 and February 2017.

He denied the charges -- which date to when he was a key figure in President Enrique Pena Nieto's 2012-2018 administration -- but faced a sentence of 10 years to life in prison if convicted.

US Attorney General Bill Barr and his Mexican counterpart Alejandro Gertz Manero said in Tuesday's statement that since Cienfuegos's arrest Mexico had opened their own probe.

They added that the decision to drop the US case was taken "in the interests demonstrating our united front against all forms of criminality."

Mexican Foreign Minister Marcelo Ebrard hailed the agreement as an "act of respect," adding that it was not a "way to impunity" for Cienfuegos.

The date of his repatriation is not yet known.

The charges against Cienfuegos appear to have arisen from witness testimony in the US trial of drug lord Joaquin "El Chapo" Guzman, who was sentenced in New York to life in prison in July 2019.