(Bloomberg) — Mexican President Andres Manuel Lopez Obrador said late Saturday that he’s working for the release of a former governor convicted of laundering money for a drug cartel, threatening to cause increased friction with the U.S.Mario Villanueva, 71, served as governor of the Caribbean state of Quintana Roo, which includes the resort city of Cancun, from 1993 to 1999. He starting serving a 22-year sentence in Mexico in 2017. Yet in May, the state Congress concluded that he was falsely accused and didn’t commit the crimes, and that his sentence was part of a political vendetta.Lopez Obrador said at an event in the state on Saturday that his government is working for Villanueva’s release, while adding that it also depends on the autonomous Attorney General’s office, where there’s an injunction to prevent it.Lopez Obrador didn’t elaborate on the reasons behind his position on the specific case, although he mentioned general backing for an amnesty bill for elderly convicts and people whose cases take years to resolve. Jesus Cantu, the information chief of the president’s press office, said that Lopez Obrador wants Villanueva freed on humanitarian grounds based on his age, a chronic lung disease and the time served on his sentence.The Villanueva case threatens to cause another irritant in Mexico’s relationship with the U.S. just days after President Donald Trump said he’s waiting for Lopez Obrador’s call to “wage war” against drug cartels after an attack killed nine dual citizens.Villanueva already served time in the U.S. after pleading guilty to laundering bribes from the Juarez drug cartel, and his release probably wouldn’t be well-received by the Drug Enforcement Administration that helped investigate him, said Alejandro Hope, a security consultant and former official for CISEN, Mexico’s intelligence agency.“This sends a strong and terrible signal of impunity,” said Gerardo Rodriguez Sanchez Lara, a professor of national security at the University of the Americas in Puebla, Mexico. “The U.S. and Mexico have worked together to punish former governors who have been involved with drug trafficking, and this is one of the few cases where there’s been punishment. The president needs to explain very clearly why he’s taking this stance.”(Updates with Mexican official’s comment in fourth paragraph.)To contact the reporter on this story: Eric Martin in Mexico City at firstname.lastname@example.orgTo contact the editors responsible for this story: Juan Pablo Spinetto at email@example.com, Kevin MillerFor more articles like this, please visit us at bloomberg.com©2019 Bloomberg L.P.