Canadian Prime Minister Justin Trudeau, in a clear jab at U.S. President Donald Trump's move to quit a major climate change pact, said on Monday the world needed "the courage to confront hard truths" on global warming.

Trudeau's remarks were the first he has made in public since Trump announced on Thursday that the United States would withdraw from the Paris accord. Trudeau issued a statement at the time saying he was deeply disappointed.

"The future is still bright for those who have the courage to confront hard truths, and the confidence to stay the course," he said in public remarks after briefly paddling along the Niagara River to mark World Environment Day.

"Canada will not back down from its commitment to fight climate change - and we are not alone. Around the world, nearly every country is on our side. ... Inaction is not an option," he added. "We can't walk away from the reality of climate change."

News of the planned U.S. withdrawal ramped up tension ahead of talks on renegotiating the North America Free Trade Agreement (NAFTA). Canada is already at odds with Washington over dairy subsidies, as well as exports of lumber and airliners.