Weekes said Canada should draw up a long list of possible targets for retaliation, and publish it for public comment in a bid to ramp up US concern about the pain of a trade war.
Mexico and Canada are among the main suppliers of steel to the US.
NAFTZ and its members have been strong supporters of the NAFTA and believe it has been an important factor in making USA manufacturing more globally competitive, supporting high-value-added employment in the United States, expanding export markets for US products and services, promoting efficient supply and value chains, and improving standards of living.
US steel and aluminum producers - and their counterparts around the world - have been hammered by overproduction by China.
Flake said the new tariffs, which function as taxes on imports, of 25% on steel and 10% on aluminum would be detrimental to the United States economy and must be stopped.
Sanders says Trump has made "very well clear" that none of the allegations are true.
The potential tariffs have caused deep anxiety among U.S. trading partners and Republican leaders in Congress.
An extension of these exemptions would be tied to progress in talks on the renegotiation of the North American Free Trade Agreement (NAFTA), the Washington Post said.
"I think that's incredibly cynical and misguided", says Edward Alden, senior fellow at the Council on Foreign Relations. Renegotiations over NAFTA began last summer. He said only that the reprieve remains in place for now and that NAFTA is important to economic and national security.
Treasury Secretary Steven Mnuchin announced at a press conference that the administration is examining the impact of imposing the tariffs on a "case-by-case" basis.
Rim countries without USA involvement, a deal that will permit, among other things, more foreign auto imports into Canada - which has already infuriated US automakers and Canada's auto workers.
Possibly. The more countries that are spared from the tariffs, the tougher the choice for the administration: Offer America's metals industries less and less protection.
Senate Majority Leader Mitch McConnell, R-Ky., says Republicans in Congress are concerned that President Trump's proposed tariffs might metastasize into a larger trade war.
The White House says Mexico, Canada and other countries may be spared from President Donald Trump's planned steel and aluminum tariffs under national security "carve-outs", a move that could soften the blow amid threats of retaliation by trading partners and dire economic warnings from lawmakers and business groups.
If the WTO threw out the USA tariffs, the president - already critical of WTO rulings against America - might be tempted to pull out of the organization.