Mexico’s ambassador to the U.S. is warning President-elect Trump that building a wall on the southwestern U.S. border would hurt the environment.

“We fear that there is going to be consequences regarding environmental issues,” Carlos Manuel Sada Solana, Mexico’s ambassador to the U.S., said in an interview with the Arizona Republic. “It’s also going to be sending a very negative message. What we say is we like to build bridges.”

Mexico has resisted Trump’s proposal, and continues to reject Trump’s demand that Mexico should be forced to pay for the wall. Sada reiterated that stance, and encouraged Trump to see Mexico as a partner, not an enemy.

“We have said time and again Mexico is not paying for the wall,” he said. “That is something that has been said several times by the president of Mexico, the secretary of foreign affairs, secretary of economy, the secretary of finance. So we are not paying for the wall.”