The US Department of Justice announced plans Tuesday to drop drug trafficking and money laundering charges against a Mexican ex-defense minister in US custody so that Mexico can do its own probe and potentially prosecute him.

Acting US attorney for the eastern district of New York Seth DuCharme asked the judge in charge of the case, Carol Amon, to release Salvador Cienfuegos from prison and send him back to Mexico escorted by marshals.

US authorities in October arrested the 72-year-old Cienfuegos at a Los Angeles airport to the surprise and irritation of Mexican officials.

Cienfuegos, a 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.

Since the arrest, prosecutors in Mexico opened their own probe, US Attorney General Bill Barr and his Mexican counterpart Alejandro Gertz Manero said in a joint statement.

"In the interests demonstrating our united front against all forms of criminality, the US Department of Justice has made the decision to seek dismissal of US criminal charges against former secretary Cienfuegos so that he may be investigated, and, if appropriate, charged under Mexican law," their statement said.

Cienfuegos pled not guilty to the charges -- which date to when he was a key figure in President Enrique Pena Nieto's 2012-2018 administration --before a New York judge last Thursday. He is due to appear before judge Amon Wednesday for a new hearing.

Court documents presented to Amon on Monday show that the US government asked her to keep the information about the dismissal of the charges secret until Wednesday's hearing, because publication "could cause harm to the government's relationship with a foreign ally."

The judge asked prosecutors for further explanation, and when she did not receive them, she decided to release the documents Tuesday night.

In the documents, DuCharme assures that Cienfuegos "will voluntarily depart the United States and be expeditiously transported to Mexico in the custody of the United States Marshals Service."

DuCharme also asked the judge that the withdrawal of the charges not go into effect until the defendant "enters and has been released in Mexico."

The United States has dropped drug trafficking and money laundering charges against Mexico's ex-defense minister Salvador Cienfuegos
The United States has dropped drug trafficking and money laundering charges against Mexico's ex-defense minister Salvador Cienfuegos AFP / RONALDO SCHEMIDT

Cienfuegos was detained at Los Angeles International Airport on October 15 while on a trip with his family, and charged with drug trafficking and money laundering.

If he had been tried and found guilty in the United States he would have faced a sentence of 10 years to life in prison.

The Mexican government complained bitterly that it was being kept in the dark about Cienfuegos's case.

The US indictment was filed in August 2019, but made public only after Cienfuegos's arrest, apparently due to suspicion of corruption among high-ranking Mexican officials.

Mexican Foreign Minister Marcelo Ebrard tweeted that under an agreement between the offices of the Mexican and US attorney generals, Cienfuegos would "be returned to Mexico to be prosecuted here if agreed by the judge in the case."

In a press conference, Ebrard hailed the move as an "act of respect."

It is "an act that we see with sympathy and, we think, is positive because we do not see it as the way to impunity but as an act of respect for Mexico and the Mexican Armed Forces," he told reporters.

He added that, in order to reach the agreement with the United States, Mexico argued that if the alleged crimes were committed in its territory, then Cienfuegos should also be prosecuted in Mexico.

At Mexico's request and working "under the Treaty that governs the sharing of evidence," the US Department of Justice "has provided Mexico evidence in this case and commits to continued cooperation... to support the investigation by Mexican authorities," the statement from Barr and Gertz read.

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