A widely followed former American diplomat questioned whether President Donald Trump was adopting the right strategy by threatening Mexico with a new tariff because of immigration issues.

Trump announced Thursday that his country plans to impose a 5% tariff on all Mexican imports from June 10. In a statement, he attributed that unexpected move to a “border crisis”.

John Negroponte questioned whether Trump’s move would have the desired effect. “I think it’s both bad politically and bad economically and I don’t think it’s really going to help solve the immigration problem, either, which is what Mr. Trump said he’s trying to attack,” said Negroponte, current vice chairman of consultancy McLarty Associates and formerly U.S. ambassador to Honduras, Mexico, the Philippines, the United Nations, and Iraq.

Mexico, for its part, has said it would not respond well to economic threats. In a letter addressed to Trump, Mexican President Andrés Manuel López Obrador said he did not want confrontation, and that leaders have a responsibility to seek peaceful solutions to controversies. “President Trump: Social problems cannot be resolved with taxes or coercive measures,” the Mexican leader wrote.

Negroponte told he agreed with that sentiment. Still, he said, perhaps now is the time that Washington and Mexico City can come together on the issue.