By David Ljunggren

CALGARY, Alberta (Reuters) - The Trump administration's main concerns about trade revolve around deficits with Mexico and China, Canada's ambassador to the United States told reporters on Sunday, saying his country was not the focus of U.S. efforts to renegotiate NAFTA.

David MacNaughton, a key Canadian player in the North American Free Trade Agreement issue, also said U.S. President Donald Trump and Canadian Prime Minister Justin Trudeau had agreed to meet "very soon."

Earlier on Sunday, Trump said he would meet Trudeau and Mexican President Enrique Pena Nieto to begin renegotiating NAFTA, under which both nations send most of their exports to the United States.

"I don't think Canada is the focus at all," MacNaughton said. "But we are part of NAFTA, and there are discussions that need to be had, and we'll be having them over the next few weeks."

MacNaughton expressed optimism that Canada would make progress in the talks.

Senior Trudeau aides in recent weeks have tried to persuade their U.S. counterparts that given the tight links between the two nations' economies, protectionist moves would hurt both Canadians and Americans.

"What we've got to worry about is that we're collateral damage," said MacNaughton.

The envoy also suggested Canada might at some point focus on bilateral relations with the United States rather than including Mexico in all the NAFTA talks.

That could upset Mexico, whose economy has suffered since Trump started expressing unhappiness with U.S. companies that have factories there.

"We will cooperate on trilateral matters when it's in our interests, and we'll be looking to do things that are in our interests bilaterally," said MacNaughton, declining to give details.

(Reporting by David Ljunggren; Editing by Peter Cooney and Lisa Von Ahn)