US President Donald Trump and his Canadian counterpart Justin Trudeau hope to reach a deal to revamp NAFTA by year's end, the White House said Thursday.

After a phone call between the two leaders that discussed the tripartite agreement between Canada, the United States and Mexico, the White House said a common target had been reached.

"The two leaders also discussed the ongoing NAFTA renegotiation and stressed their hope to reach an agreement by the end of this year," a White House statement said.

Trump had earlier suggested that he could soon begin the process of terminating the North American Free Trade Agreement, accusing Mexico of "being difficult" in talks to rework the decades-old deal.

"NAFTA is one of the worst trade deals ever signed at any time anywhere in the world, and I can understand why Mexico is being difficult, because why wouldn't they be? They've had it their way," Trump said on Monday.

The three countries will resume their negotiations on Friday in Mexico City.