This comes as Washington upped the pressure on its neighbors to reach a deal on the North American Free Trade Agreement (NAFTA) by May 1 or face tariffs on steel and aluminum.

"The minister will remain in Washington for all of Thursday to continue NAFTA negotiations," Freeland's spokesman Adam Austen told AFP.

She will be represented at the NATO meeting by her parliamentary secretary, Omar Alghabra.

Major differences remain to be settled in the NAFTA negotiations, but Freeland said late Wednesday that good progress had been made on the issue of auto parts.

She also underscored Canada's strong objection to inserting a clause into the agreement that would allow a party to exit the pact after five years, saying it would create uncertainty for investors.

Earlier, senior White House advisor Larry Kudlow said the United States would continue to exempt allied economies from new steel and aluminum tariffs -- if they make concessions on trade.

Canada and Mexico -- as the main suppliers to the US -- had been exempted indefinitely from the punishing import duties of 25 percent on steel and 10 percent on aluminum.

But Washington on Thursday lumped them in with the EU, Brazil, South Korea and others in an order lifting the exemptions at month's end.

The parties had previously said they hoped to reach a new NAFTA deal before campaigning revs up for US midterm and Mexican presidential elections later this year.

The latest US move to push for a quick deal comes also as the United States now looks to focus on its trade disputes with China.

Its chief NAFTA negotiator, US Trade Representative Robert Lighthizer, is to travel next week to Beijing for talks.

US President Donald Trump triggered renegotiation of NAFTA last year after labeling it a "disaster" that has destroyed US jobs. He has repeatedly threatened to leave the pact if a satisfactory deal is not reached.