Mexico’s foreign-affairs secretary had strong words for U.S. President Trump on Tuesday, criticizing his plans for a wall on the U.S.-Mexico border as a “bad idea” that will only ruin relations. Foreign Affairs Secretary Luis Videgaray reiterated Mexico’s stance that the U.S. should pay for the wall, saying the Mexican side will not pay a dime for it. Trump has already walked back his earlier promises to make Mexico foot the bill, hinting this week that he might wait until the fall to seek approval from Congress for funding. In an apparent tit-for-tat move, Videgaray also said the Mexican government is considering charging Americans a fee to enter, though he didn’t provide any details on that initiative. Setting the tone for upcoming talks between the U.S. and Mexico on trade and immigration, Videgaray warned that Mexican authorities could cut back cooperation with the U.S. in one of the most important spheres of bilateral relations. “If the negotiation on other themes—immigration, the border, trade—isn’t satisfactory to Mexico’s interests, we will have to review our existing cooperation,” Videgaray said Tuesday, the Associated Press reported. “This would be especially in the security areas... and that involves the national immigration agency, the federal police, and of course, the armed forces,” he said. Mexico now assists U.S. law enforcement in dealing with drug cartels and drug trafficking.