Bernie Sanders said he would “immediately begin renegotiating” the new trade agreement between the U.S., Mexico and Canada on his first day in office as president.

Sanders has long opposed the U.S.-Mexico-Canada Agreement, known as USMCA, which President Donald Trump signed into law Wednesday. The Vermont senator was the only candidate to say he opposed the deal during the last debate of Democratic presidential contenders. Sanders says the agreement does not address climate change or provide sufficient labor protections.

“The NAFTA 2.0 that Trump signed today is an absolute disaster,” Sanders said in a statement. “In addition to doing nothing to stop the offshoring of jobs, the deal is a giveaway to the fossil fuel industry at a time when climate change threatens our planet.”

He also said the deal does nothing to prevent companies like Exxon Mobil Corp. and Chevron Corp. from dumping waste and pollution in Mexico.

“It does not even mention the words ‘climate change,’ the most existential threat facing our planet,” Sanders said.

Senator Elizabeth Warren, Sanders’ rival for the Democratic nomination, initially joined him in criticizing the deal. During a 2018 speech on foreign policy at American University in Washington, she said the agreement, as written, wouldn’t halt outsourcing, raise wages or create jobs. But in January, she announced she would vote for it. Her campaign said revisions to the deal dropped a provision that would make it harder to bring down prescription drug prices, and offered stronger labor standards and more certainty for farmers.

Another candidate, Senator Amy Klobuchar of Minnesota, said in December she would vote for the pact. A day later, her moderate rival, former Vice President Joe Biden, joined in support, emphasizing the elimination of loopholes for drug companies and strengthening enforcement for labor and environmental standards.

“What I’ve seen change is that the vast majority of the labor movement supported it,” Biden told reporters in Los Angeles.

Since Dec. 10 -- when House Speaker Nancy Pelosi announced that she had struck a deal with the White House to pass the USMCA -- the S&P 500 Index has gained about 4.6 per cent and the Dow Jones Industrial Average has improved more than 3 per cent. Markets were also bolstered during that period by a “phase one” trade deal with China.

(Disclaimer: Michael Bloomberg is also seeking the Democratic presidential nomination. He is the founder and majority owner of Bloomberg LP, the parent company of Bloomberg News.)