Mexico’s president called Donald Trump “a friend” Friday and said he would write to the former U.S. president to warn him against pledging to close the border or blaming migrants for bringing drugs into the United States.

President Andrés Manuel López Obrador called Trump “a man of intelligence and vision,” despite Trump’s repeated calls to close the two countries’ border.

López Obrador said that in a letter he planned to send next week, “I am going to prove to him that migrants don’t carry drugs to the United States,” adding that “closing the border won’t solve anything, and anyway, it can’t be done.”