A leading business group of CEOs said Tuesday that withdrawing from the North American Free Trade Agreement (NAFTA) would cost U.S. jobs and hurt the economy.

A new economic analysis for the Business Roundtable shows that the net loss of U.S. jobs would total 1.8 million within the first year, according to the study, which was prepared by Trade Partnership Worldwide.

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Leaving the three-nation deal would reduce U.S. exports to Canada and Mexico by 17.4 percent each, lower American companies' global exports by 2.5 percent and diminish the purchasing power of the average U.S. household by nearly $654 because of higher prices and lower wages caused by increased tariffs, the study showed.

"Terminating NAFTA would permanently reduce U.S. employment, exports, and economic output, while benefiting our economic competitors at the expense of American workers and businesses," said Joshua Bolten, president and CEO of Business Roundtable, in a statement.

"We urge the administration to take into account the potential damage of withdrawing from NAFTA, and to focus instead on modernizing the agreement so that it remains a cornerstone of American prosperity,” Bolten said.

The study also showed that a U.S. breakup with Canada and Mexico would shift economic activity away from North America and toward economic competitors, including China, which would get a boost in growth and employment.

President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE has said repeatedly that he will pull the United States out of the NAFTA deal if the nation doesn't reach a deal that provides more benefits.

The study was released as Mexico, Canada and the United States gather in Montreal for the sixth round of NAFTA negotiations.

Also on Tuesday, Canadian Prime Minister Justin Trudeau announced that a deal had been reached with 10 other Pacific Rim nations on a reshaped Trans-Pacific Partnership (TPP) agreement that doesn't include the United States.

Trump left the TPP deal a year ago, shortly after taking office.