Who said anything about tarrifs? He’s talking about renegotiating.
He's talking about renegotiating to allow tariffs.
Watch the video (not linked here, but if you google the headline, you'll find it). The whole discussion of NAFTA arose out of a discussion of tariffs. Trump said he would impose tariffs on Ford if Ford built a plant in Mexico. The interviewer asked how he could do that, since NAFTA prohibits such tariffs. Trump said he'd renegotiate or break NAFTA.