NAFTA, Trump said again today (Aug 27), was a “ripoff,” and Canada would have to scramble to to negotiate to join the new deal—which he dubbed the US Mexico Trade Agreement—or face tariffs on all cars it exports to the US.

“We’ll give them a chance to have a separate deal, or we could put it into this deal,” Trump said.

It sounds bad for Canada, but what, exactly, have the US and Mexico committed to? Less than it looks like, trade experts say.

The White House press event was another Trump presidency trade moment that was heavy on threats and light on substance (not to mention marred by a glitchy conference call with Mexican president Enrique Peña Nieto.)

Trump can’t just unilaterally scrap the 25-year-old NAFTA deal, even on behalf of the US. Changes the administration has been re-negotiating for months require congressional approval.

In fact, the negotiations with Mexico aren’t yet finalized, the US Trade Representative confirmed later. The US’s top trade representative, Robert Lighthizer, is expected to file documents Aug. 31 that would include specifics.

Then Congress has 90 days to read and approve the details, thanks to Trade Promotion Authority rules, a process that could extend past the contentious mid-term elections. There’s no guarantee Trump’s Republicans will hold its majority in the House.

Republicans are eager to make sure that Canada is included in a new trade deal. Orrin Hatch, the Utah senator who chairs the Finance Committee that would need to approve any deal, stressed that “a final agreement should include Canada.”

Any changes to NAFTA deal require Canada’s approval, as foreign minister Chrystia Freeland’s office pointed out. Freeland, who is traveling to Washington DC tomorrow (Aug. 28) to continue negotiations, “will only sign a new NAFTA that is good for Canada and good for the middle class,” her office said. “Canada’s signature is required,” for any renegotiation, it noted.

The Mexican president was sure to add he was “quite hopeful” that Canada will start discussing “sensitive bilateral issues” with the US. Canadian and Mexican officials are believed to be working together under a “gentlemen’s agreement” that neither would sign a deal with the US without including the other, said Nick Anstett, a director at Albright Stonebridge Group, which consults for global businesses.

Trump’s threat that he will tax car imports unless Canada agrees to lower tariffs on dairy products appears to be an empty one. Canada doesn’t have any major homegrown vehicle brands. Many of the cars made there last year were models made for the US’s big automakers Ford, GM, and Chrysler, according the Canadian government:

Putting a tariff on GM’s Cadillacs would only make them more expensive for US consumers, and cut into US companies’ profits.