Texas' decision to deploy National Guard troops along its border with Mexico is "unpleasant" and "reprehensible," Mexican President Enrique Pena Nieto says.
Last month's deployment had previously drawn the ire of Mexico, which says the border should not be militarized and issues should be solved jointly.
In an interview with the newspaper El Universal published Friday, Pena Nieto said Texas' move could affect bilateral relations.
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Texas Gov. Rick Perry has criticized border security and suggested last month that Islamic terrorists could be entering the U.S. from Mexico. Mexico has dismissed that idea as "absurd."
Texas maintains it needs to deploy National Guard troops to stop drug traffickers. The number of Central American migrants entering Texas also spiked earlier this year, but the flow has since declined.
Gov. Perry's spokeswoman, Lucy Nashed, said the guard had been sent to the border "to disrupt criminal activity that threatens all American citizens."
"Rather than questioning Gov. Perry's decision to do what he knows is right for the citizens of his state and country, we wish the Mexican government would instead work more cooperatively with us to address this very serious problem," she said.