By ROB GILLIESTORONTO (AP) — Canada's ambassador to Washington said Wednesday that Canada is open to renegotiating the North American Free Trade Agreement if that's what President-elect Donald Trump wants. Ambassador David MacNaughton, on a conference call with journalists, said free trade on lumber, long an irritant, would be one of the first things he'd like to see if there's a new agreement. He noted that the U.S. is Canada's largest trading partner and Canada is the largest trading partner for the U.S. "We're ready to come to the table," he said. Canadian Prime Minister Justin Trudeau spoke to Trump on Wednesday night to congratulate him and to invite him to Canada at the earliest opportunity. Trump also invited Trudeau to visit him. "The Prime Minister and the President-elect reiterated the importance of the Canada-United States bilateral relationship, and discussed various areas of mutual interest," Trudeau's office said. The Liberal prime minister has vowed to work "very closely" with Trump and said Canada has no closer ally and partner than the United States. But Trudeau's openness to trade, refugees and the environment stands in stark contrast to Trump. Of particular concern to Canada is Trump's vow to renegotiate NAFTA but MacNaughton said any agreement can be improved. Trump has called NAFTA the "worst deal in history." MacNaughton said if NAFTA was scrapped, the original Canada-U.S. trade agreement that predated NAFTA would come back into force and he said he doubted the Americans would want to end that. A positive for Canada could be the eventual approval of TransCanada's Keystone XL pipeline from Alberta to the U.S. Gulf Coast. President Obama nixed it but Trump supports the pipeline though he has said he wants a share of the profits. TransCanada said it remains committed to building the pipeline. Brad Wall, premier of the Canadian province of Saskatchewan, noted Trump's support for Keystone XL.