The United States, Canada and Mexico will promise on Wednesday to generate half their overall electricity from clean energy by 2025, the White House said.

"We believe it is an aggressive goal, but that it is achievable continent-wide," Brian Deese, senior advisor to US President Barack Obama, said Monday.

He spoke during a telephone conference call with reporters two days ahead of a summit between the three countries' leaders in Canada.

In 2015, clean energy -- wind, solar and hydropower, plus nuclear power -- accounted for 37 percent of the three countries' electricity, he added.

In the United States, the region's largest electricity producer by far, clean energy currently generates around a third of total output, putting it behind Canada but ahead of Mexico.

The rise in the coming years will be "principally driven by renewables and energy efficiency," Deese said.

In Canada, hydropower generates some 59 percent of electricity and nuclear power another 16 percent.

Mexico will also join an existing commitment by the United States and Canada to reduce production of methane, a potent greenhouse gas, by 40 to 45 percent of its 2012 level by 2025.

Canadian Prime Minister Justin Trudeau and his guests Obama and Mexican President Enrique Pena Nieto will meet in Ottawa for the North American Leaders Summit Wednesday morning under a climate of economic uncertainty following Britain's vote to leave the European Union on Thursday.

Linked by the North American Free Trade Agreement (NAFTA) since 1994, the three countries usually hold an annual summit dubbed the "Three Amigos."

Chaired for the first time by Trudeau -- leader of Canada's Liberal Party -- following his election in November, the summit will also be Obama's last before he steps down in January.

The two met in March during Trudeau's visit to Washington, which marked a distinct warming in relations following a decade of Canadian rule by Trudeau's conservative predecessor Stephen Harper, who showed little interest in the fight against climate change.