Negotiators hope to come to a deal as soon as the end of the day.
"Force majeure" language is common in contracts, but rare in trade agreements, and was possibly another missed sign of the coronavirus outbreak in China last year.
But Republicans are far less skeptical of trade pacts than they were before his presidency.
President Donald Trump said the signing as a way of delivering economic justice for American workers.
They agree on a lot more than they disagree, but the debate pointed out a key difference.
In a split with progressive rival Bernie Sanders, the Massachusetts senator pledged her vote for a reworked NAFTA pact.
The Conservative Party has a new base — and possibly a new approach.
Pelosi called the new U.S.-Mexico-Canada agreement "much better than NAFTA."
The president's claim came after markets plunged, apparently in response to Trump's remarks that his trade war with China may persist.
Democrats don't think the U.S.-Mexico-Canada trade deal should get tangled up in impeachment.