By Gabriel Stargardter

MEXICO CITY (Reuters) – Mexico is in talks with the United States on whether to allow U.S. federal air marshals to travel with Taser stun guns on cross-border flights with U.S. airlines, National Security Commissioner Renato Sales said in a TV interview on Tuesday.

Sales’ comments come the day after Reuters exclusively revealed that Mexico and the United States were looking into an agreement that could allow armed U.S. federal air marshals to be deployed on commercial cross-border flights.

Mexico has been trying to prove itself a good ally to the United States in hopes this will help its efforts to renegotiate the North American Free Trade Agreement (NAFTA) in terms that are as favorable as possible.

In his interview with broadcaster Televisa, Sales said no memorandum of understanding had been signed with the United States, adding that talks to allow U.S. federal marshals in Mexico stretch back years.

“They would only be on commercial (U.S.) flights, on (U.S.) airlines, not on Mexican airlines,” he said. “But it’s still not finalized … we’re still in talks.”

Reuters reported on Monday that the hardest part of the negotiations would center on allowing U.S. officials to carry arms, given that the use of weapons by foreigners in Mexico is sensitive and tightly regulated.

Sales said he understood that the U.S. federal air marshals would carry stun guns, not lethal weapons, and said they would be undercover, but did not give any further details.

It was still not clear if the air marshals would fly on just U.S.-bound flights, Mexico-bound flights, or both.

The U.S. Department of Homeland Security (DHS) places sharp-shooters on certain domestic and international commercial flights to and from the United States to prevent militant attacks.

In a statement on Monday, Mexico’s foreign ministry confirmed that the government was evaluating the plan’s potential operational and security benefits but added that no agreement has yet been reached.

The foreign ministry has pushed hard to defend NAFTA ahead of a July 2018 election in which the ruling Institutional Revolutionary Party (PRI) is currently polling third.

Mexico, Canada and the United States are currently engaged in fraught negotiations to reshape NAFTA, a lynchpin of the Mexican economy that Trump has threatened to abandon.

(Reporting by Gabriel Stargardter; Editing by David Gregorio)