MEXICO CITY, Sept 19,  (AP): Mexican President Andrés Manuel López Obrador on Wednesday demanded that former Secretary of Public Security Genaro García Luna, who was convicted on drug trafficking charges in the United States last year, present evidence to support his accusations that the president has links to drug trafficking.

López Obrador was responding to a jailhouse letter from García Luna that his attorney distributed to the press. García Luna alleged contact between López Obrador and the faction of the Sinaloa cartel led by Ismael "El Mayo” Zambada, who was arrested in July in Texas. The letter comes just weeks before López Obrador leaves office and after earlier allegations that López Obrador's previous presidential campaign took contributions from drug traffickers.

"He writes that there is proof, there are videos, there are calls, there are audios. It’s very simple, he should share them with the public,” said López Obrador in his morning news briefing. "He needs to show proof,” said the president. He suggested that he ask, "his friends at the DEA.” García Luna was convicted last year of taking massive bribes to protect the violent drug cartels he was tasked with combating.

In the letter, he maintained his innocence. Garcia Luna served in different security posts under former presidents Vicente Fox and Felipe Calderón between 2000 and 2012. Both are political enemies of López Obrador. He said in the letter that Mexican and U.S. officials have proof. "There are contacts, videos, audios, photographs, communication and management records between current Mexican President Andrés Manuel López Obrador and his operators with drug trafficking leaders and their families, in particular drug traffickers who were used as witnesses against me in my trial," wrote García Luna.

The 56-year-old former top Mexican security official faces a sentence of 20 years to life in prison. His sentencing is scheduled for Oct 9. Denying the accusations against him, García Luna accused the Mexican government of "lying” and "giving false information” about his case to the United States. He claimed in the letter that US prosecutors offered him a deal to become a protected witness in exchange for a six-month sentence.