WASHINGTON – The U.S. Justice Department asked a federal judge to drop the drug trafficking charges against Chinese-born Mexican pharmaceuticals importer Zhenli Ye Gon.

The request, which would open the door for Gon’s extradition to Mexico, was filed after prosecutors encountered “evidentiary concerns.”

The Justice Department told the judge that Gon should be tried in Mexico because the case “is of considerable public interest and is important to Mexico’s counter-narcotics policy.”

In the documents, it states that one of the key witnesses in the case had withdrawn his statements and that another had been unwilling to provide testimony.

Gon, now 46, was arrested in July 2007 by U.S. Drug Enforcement Administration agents at a restaurant in suburban Washington and a federal grand jury formally accused him of “conspiracy to aid and abet the manufacture of 500 grams or more of methamphetamine, knowing that it would be imported into the United States.”

“The defendant ... has been arrested in connection with the seizure of more than $205 million in drug money,” Assistant Attorney General Alice Fisher said in July 2007.

Gon’s pharmaceutical firm, according to the indictment, acquired chemicals used to produce methamphetamine, or “crystal meth.” Mexican authorities said the $206 million discovered in March 2007 at the mogul’s Mexico City residence represented his profit from dealings with drug cartels.

This week’s decision by the Justice Department was criticized by U.S. District Judge Emmet Sullivan, who ordered prosecutors to present documents in which they explain why they delayed so long in revealing problems with the evidence against Gon.

Sullivan said prosecutors “ought to resign” if they considered themselves exempt from rules requiring that certain types of evidence have to be turned over to defense lawyers, the Washington Post reported.

Manuel Retureta, one of Gon’s lawyers, said that he was satisfied with the decision of the Justice Department, but he added that his next task is to try and impede his client’s extradition to Mexico to face similar charges.

The discovery of the enormous cash hoard at Gon’s residence was presented by the Mexican government as a great coup in the war on drugs.

But Gon maintains that $150 million of the money was part of a slush fund belonging to Mexico’s right-wing National Action Party, or PAN, the organization of incumbent President Felipe Calderon and his predecessor, Vicente Fox.

Prior to Mexico’s July 2006 presidential election, Gon says, unnamed individuals came to his office and forced him to accept suitcases stuffed with cash for safekeeping.

Gon’s accusations have been repeatedly rejected by Calderon and other members of his administration as both false and “ridiculous,” but even some PAN lawmakers joined other members of the Mexican Congress in calling for a probe of the affair.

Attorneys for Gon have claimed to be in possession of audio- and videotapes implicating Mexican politicos in illicit activities. EFE