OTTAWA (REUTERS) - Canadian Prime Minister Justin Trudeau urged US President Donald Trump not to withdraw from Nafta in a call on Wednesday, saying such a move would be counter-productive, a Canadian source familiar with the matter said on Thursday (April 27).

Trudeau made the comments after Trump told him he was thinking about pulling out of the North American Free Trade Agreement and asked for his opinion, said the source, who asked to remain anonymous given the sensitivity of the situation.

The White House said earlier that Trump told the leaders of Canada and Mexico on Wednesday that he would not terminate the Nafta treaty at this stage, but would move quickly to begin renegotiating it with them.

"Trump told him (Trudeau) he was thinking about withdrawing from Nafta and said he wanted our opinion," said the source. "The Prime Minister told him a US withdrawal would cause job loss and instability on both sides of the border. He said he understood his frustration with Congress, but that this step would be counter-productive," the source added.

Trump's administration has yet to formally advise Congress of its intention to open negotiations.

Any move to break up Nafta would cause great economic damage to Canada, which sends 75 per cent of all its exports to the United States.

Trudeau, according to the source, reiterated to Trump that Canada was open to a discussion about how Nafta could be improved.

Canadian officials have so far taken a largely restrained attitude to Trump's harsh language on Nafta, describing it as a negotiating tactic ahead of the talks.