Mexican President Claudia Sheinbaum said on Monday that her government told the United States in a diplomatic note that the unauthorized presence of U.S. officials at an anti-narcotics operation in the northern state of Chihuahua should not be repeated.
The incident came to light after two U.S. officials, along with two Mexican officials, were killed in a car crash on April 19 after the operation. Sheinbaum has said the federal government was not aware of the participation of the U.S. officials, who sources told Reuters were CIA officers.
"What we told [the U.S.] was that the federal government didn't know about the involvement of these people [in the operation], and we hope that it's an exception," Sheinbaum said in her daily morning press conference.
Mexico requested that "from now on, as has been done, our constitution and national security law should be followed," Sheinbaum added, saying that the U.S. had indicated its agreement.
On Saturday, Mexico's security cabinet said in a statement that the U.S. officials lacked formal accreditation to participate in security activities in Mexico and that one of them had entered the country as a tourist.
The deaths of the two Americans rekindled U.S.-Mexico tensions over security cooperation. The presence of U.S. personnel in anti-cartel operations is a deeply sensitive matter in Mexico.
Sheinbaum has long maintained that she welcomes intelligence sharing and security cooperation but will not accept U.S. agents or forces participating in operations in Mexican territory.
In contrast, President Donald Trump has repeatedly called for greater use of U.S. military force to combat Mexican cartels and has threatened that the U.S. could go it alone if Washington feels Mexico isn't doing enough.
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