“We are not going to pay any single cent for such a stupid wall! And it’s going to be completely useless,” said former Mexican president Felipe Calderón when asked about this at the AmCham Egypt for Business Conference on Sunday.

Calderón told CNBC’s Hadley Gamble his country will not be funding the construction of the wall, also adding that while Trump blames Mexican migration for the majority of illegal immigration into the U.S., the net migration between the countries has flipped. According to a Pew Research report in November, more Mexicans were emigrating from the U.S. than entering.

“The first loser of such a policy would be the United States,” he added. “If this guy pretends that closing the borders to anywhere either for trade [or] for people is going to provide prosperity to the United States, he is completely crazy.”