Former Canadian Prime Minister Stephen Harper said U.S. President Donald Trump may quit the North American Free Trade Agreement unless he can get a solid win that would demonstrate American workers will benefit.

“I don’t think that it’s going to be adequate for President Trump to have an agreement that he can’t in some concrete way say is going to improve the lives of some of these masses of people who voted for him,” Harper said in Washington Wednesday during a panel hosted by the Dentons law firm. “It has to be a lot more than some kind of technical revamp and I think that’s going to be tough to get to.”

It is “conceivable” that Trump would quit Nafta, said Harper, who led Canada for a decade before Justin Trudeau was elected in 2015. “Donald Trump would be willing to take the economic and political risks of that under some circumstances.”

“If I were a business on this, I would be trying to understand what the consequences would be for my business in the event of a cancellation.”