President Donald Trump says he thinks the U.S. will “end up probably terminating” the North American Free Trade Agreement with Canada and Mexico “at some point.”

Trump tells supporters at a Phoenix, Ariz., rally that, “Personally, I don’t think we can make a deal because we have been so badly taken advantage of.”

But he cautions he has yet to make up his mind.

The U.S., Mexico and Canada began formal negotiations to rework the 23-year-old trade pact that Trump slammed during his campaign as the “worst” in history.

The Canadian and Mexican negotiators believe NAFTA needs to be updated. But they have defended the pact, which eliminated most barriers on trade between the countries, as an economic success story.