Auto stocks soared and financial markets firmed on the expectation that Canada would sign on to the deal by the end of the week and ease the economic uncertainty caused by U.S. President Donald Trump's repeated threats that he would ditch the 1994 accord.

But details of gains and concessions in the deal were only starting to emerge on Monday, and Trump threatened he still could put tariffs on Canadian-made cars if Canada did not join its neighbors.

"I think with Canada, frankly, the easiest we can do is to tariff their cars coming in. It's a tremendous amount of money and it's a very simple negotiation. It could end in one day and we take in a lot of money the following day," Trump said.