"The president’s apparent willingness to move on without Canada prompted confusion and concern among lawmakers — who said it may not be legally permissible, let alone smart — and businesses whose supply chains depend on a deal encompassing all three countries."

" Any agreement that does not involve Canada is likely to face legal challenges and intense opposition from Congress, which had granted the Trump administration authority to renegotiate Nafta as a trilateral deal."

"We will only sign a new Nafta that is good for Canada and good for the middle class,” Mr. Austen added. “Canada’s signature is required.”

“Nafta is a trilateral agreement. It requires legislation and a change to Nafta requires legislation,” said Senator Patrick J. Toomey, Republican of Pennsylvania. “I’ve told them any change has to go through Congress. There is not necessarily complete agreement about that.”