MEXICO CITY (Reuters) - Mexico’s president said on Monday the U.S. government understood his administration’s stance on the case of ex-defence minister Salvador Cienfuegos, who Mexico decided not to prosecute after U.S. authorities had built a case against him. Speaking at a news conference, President Andres Manuel Lopez Obrador said Washington understood that Mexico had to defend its authority and prestige in the matter of Cienfuegos, whom U.S. prosecutors had accused of working with drug traffickers. Cienfuegos has denied any wrongdoing. The Mexican attorney general’s office said last week the U.S. case was not strong enough to warrant charges against Cienfuegos, who was defence minister in the previous government, and was initially arrested by U.S. officials in October. Citing diplomatic considerations, U.S. authorities released Cienfuegos in November, and Mexico initially said it would take up the case against the retired general before dismissing it. Lopez Obrador said the case against Cienfuegos was full of errors and contradictions, and last week he ordered the U.S. files on the investigation to be made public. The U.S. Justice Department expressed dismay at the publication of those files and the decision not to charge Cienfuegos, sparking concern that bilateral relations and security cooperation could suffer as a result. Lopez Obrador said relations would be “very good” with President-elect Joe Biden after he takes office this week.