Mexico’s president on Friday urged the United States to shed light on a gun-running sting that caused bilateral friction under the Obama presidency, questioning the behaviour of past U.S. administrations for the third time this week.

Mexican President Andres Manuel Lopez Obrador said his government would send a diplomatic note to Washington for information on the 2009-2011 operation known as ‘Fast and Furious,’ a topic that has resurfaced in recent days amid a debate over historic U.S.-Mexico cooperation on security and possible corruption under previous administrations.

Setting out to stop cross-border gun smuggling, the U.S. scheme allowed people to illegally buy arms in the United States and take them to Mexico so that the weapons could be tracked and lead law enforcement officials to drug cartel bosses. Some weapons were later blamed for gangland slayings in Mexico.

“How could this be? A government that invades in this way, that flagrantly violates sovereignty, international laws,” Lopez Obrador said at his daily news conference.

To avoid a repeat, the matter needed to be cleared up, said Lopez Obrador, who noted that President Donald Trump had last year been “respectful” to Mexico in discussions over joint co-operation following two major security incidents.

Mexican politicians are still arguing over how much its government knew about ‘Fast and Furious’ at the time.

Lopez Obrador brought up the gun-running scheme on Monday when discussing the case of Genaro Garcia Luna, Mexico’s security minister from 2006-12, who was arrested in the United States in December and charged with drug-trafficking offenses. As security minister, Garcia Luna had spearheaded a crackdown on drug gangs, launched under former President Felipe Calderon.

Roberta Jacobson, a former American ambassador to Mexico appointed under U.S. President Barack Obama, had suggested both governments knew about possible corruption by Garcia Luna in an interview with Mexican magazine Proceso published at the weekend.

Lopez Obrador has used the arrest of Garcia Luna to argue that corruption was rampant in past Mexican governments.

But this week he has also asked whether previous U.S. administrations were complicit by working with Garcia Luna, whose period as minister coincided with Obama’s first term in office and the final years of George W. Bush.

ELECTION

Critics of Lopez Obrador contend that he has done Trump a favor by raising questions about Garcia Luna as the U.S president prepares to fight a November election against Joe Biden, who was vice president from 2009 to 2017 under Obama.

Fernando Belaunzaran, co-leader of the opposition Party of the Democratic Revolution, on Twitter called it a “badly-disguised” stunt by Lopez Obrador to curry favor with Trump ahead of a joint meeting the Mexican president has proposed.

Allies of Lopez Obrador reject this, saying instead that he is seeking to put pressure on Calderon, a critic of the president who is building a new political party.

“This (diplomatic) note is about domestic political matters,” said Lorenzo Meyer, a historian at the Colegio de Mexico and longtime supporter of the president. “I don’t think he’s given thought about what this means for the United States.”

On Monday, Lopez Obrador said U.S. officials at the Drug Enforcement Administration (DEA), the Central Intelligence Agency (CIA) and the Federal Bureau of Investigation (FBI) who cooperated with Garcia Luna should be investigated.

The DEA and the CIA declined to comment. The FBI did not immediately respond to a request for comment.

On Thursday, Lopez Obrador again asked for U.S. officials to be investigated for their ties to Garcia Luna, saying “cover-ups” during the era were not the work of just “one government.”