Trump celebrates as he signs USMCA trade agreement

"Today we are finally ending the NAFTA nightmare," Mr. Trump added, referring to the North American Free Trade Agreement, which was the precursor to the USMCA deal.

"This is a colossal victory for our farmers, ranchers, energy workers, factory workers, and American workers in all fifty states," the President said.

How much new economic growth the deal will spur is the subject of differences among economic experts.

The President predicted the deal will boost the Gross Domestic Product of the U.S. by 1.2 percent - but trade experts in the Trump Administration have pegged the number at about one-third of that prediction.

Government experts also say the President's higher tariffs on imports from China, Europe, and more will hold back on economic growth, possibly offsetting any gains from the USMCA deal.

No matter the final outcome, Republicans heralded the final approval of the plan, which seems certain to be frequently talked about on the 2020 campaign trail by the GOP, and the President.

"It includes a cutting-edge digital trade chapter that will bring North American commerce into the 21st Century," said Sen. Rob Portman (R-OH).

One thing which was missing at the signing ceremony were Democrats in the Congress, who voted overwhelmingly for the deal in both the House and Senate.

“The original USMCA draft put forward by the Trump Administration left American workers exposed to losing their jobs to Mexico, included unacceptable provisions to lock in high prescription drug prices and fell short of key environmental standards,” Speaker Nancy Pelosi said earlier this month, as Democrats said they were fine with not being invited to the White House.