The two United States trading partners have threatened retaliation unless they are exempted from the planned tariffs, which have rattled financial markets.
Canada, the biggest supplier of steel and aluminum to the US, and Mexico, the No. 4 source of steel, have asked to be excluded, and both indicated they will strike back if Trump includes them in the stiff duties.
The tariffs would also hit other USA allies - Britain, Germany, South Korea, Turkey and Japan.
The International Monetary Fund also expressed concern about the proposed tariffs and said they likely would damage the US economy as well as the economies of other nations.
He is being repeatedly pressed on the Canada issue in these interviews.
Contrary to his apparently conciliatory tone at the World Economic Forum in Davos, last Thursday's announcement of steep metal tariffs leaves no one in doubt about the meaning of U.S. President Donald Trump's "America first" agenda.
A spokesperson for 10 Downing Street said the United Kingdom is "engaging" with the U.S. on what Mr Trump's tariff announcement means in practice. Of special concern to Canada is the auto industry - and how these tariffs would play havoc with cross-border supply chains.
"Obviously this is the time for cool heads but it is also a time for governments around the world - and alternative governments - to point to dangers of this sort of protectionism and the benefits of trade".
A U.S. official said on Friday possible exemptions would be considered case-by-case. Canada would say, 'National security exemption?
"China wins when we fight with Europe", he said on CBS's "Face the Nation".
Trump thumbed his nose Friday at the concerns over rising trade tensions and higher prices for USA consumers, tweeting that "trade wars are good, and easy to win". Canadian Trade Minister Francois-Phillippe Champagne called tariffs "unacceptable", according to the news site, adding a pledge to defend Canadian workers in the steel and aluminum industry.
"I am very optimistic", Marshall told reporters after briefings from USA trade officials.
He refuted reports that increase in import tariff on steel would hurt American industries in particular the vehicle manufacturing industry.
"The US has an $800 Billion Dollar Yearly Trade Deficit because of our "very stupid" trade deals and policies", he said.
Meanwhile Europe has reacted with similar annoyance, feeling it has been caught up in a move against China, where the E.U.is as much a victim as the USA from emerging market dumping.
However, the United States maintains a trade surplus with Canada of almost $8 billion in 2016, and in the first nine months of 2017 the surplus was almost $3 billion.
Ryan spokeswoman AshLee Strong said in a statement, "We are extremely anxious about the consequences of a trade war and are urging the White House to not advance with this plan". Dudenhöffer cited figures showing that Fiat Chrysler imported more than 45 percent of its total cars sold in 2017, while General Motors imported some 25 percent.