Mexico President Claudia Sheinbaum said Wednesday that surveillance drone flights by the U.S. government over Mexico are occurring in collaboration with and at the request of her government.

They come as U.S. President Donald Trump's administration has increased pressure on Mexico to do more to stop the production of the synthetic opioid fentanyl that is smuggled north to the United States.

Earlier this month, Trump threatened, then postponed 25% tariffs on Mexican imports that he said were meant to push Mexico to take more action against its drug cartels. Trump also ordered on his first day in office the designation of some of Mexico’s drug cartels as foreign terrorist organizations. Those designations will be published in Thursday’s edition of the Federal Register, according to a notice Wednesday.

Mexico responded to the tariff threat by sending 10,000 National Guard troops to the northern border.

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The drone flights were reported Tuesday by the New York Times as a Central Intelligence Agency program aimed at locating fentanyl labs in northwestern Mexico. The flights follow U.S. military statements that it had increased surveillance capabilities along the countries’ shared border. The CIA declined to comment in response to questions about the drone flights.

Mexico’s Defense Secretary Ricardo Trevilla addressed the flights by U.S. military planes last week, saying that they had not entered Mexican airspace, but that he couldn’t rule out they were spying because he didn’t know what they were doing.

Sheinbaum on Wednesday presented a more detailed explanation.

“These flights are part of the coordination … collaborations that have been going on for many years, between the United States government and the Mexican government,” Sheinbaum said at her daily press briefing. “Every time it is at Mexico’s request for collaboration, for information to be able to attend to security conditions.”

She said the information gathered was shared with Mexican authorities.