Canada and the European Union have already vowed to introduce their own countermeasures and Mexico, China and Brazil said they were also considering retaliation. "We had a very bad deal with Mexico, we had a very bad deal with NAFTA", the North American Free Trade Agreement with Mexico and Canada.
On Saturday, Trump threatened European automakers with a tax on imports if the European Union retaliates.
Trump did not provide many details in a pair of tweets, except to say that Canada "must treat our farmers much better", while Mexico "must do much more on stopping drugs from pouring into" the United States. "What possible scenario could you envision where we wouldn't supply you with steel and aluminum?"' "Massive relocation of companies & jobs", Trump wrote.
The official explained that there would be virtually no increase in cost of cars in the country as a result of the new aluminum tariffs.
Bolten praises Trump for following through on campaign promises to cut taxes and federal regulations, but trade is another matter.
"The U.S.is the second-biggest exporting market after China for Japanese aluminium producers and the high duties will directly impact on their business", he said.
Trump has said he plans to slap a 25-percent tariff on steel imports and 10 percent on aluminum next week.
Katainen, who handles trade policy for the EU with European Commissioner for Trade Cecilia Malmstrom, said he understood that the United States was seeking to take a stand against China, which has flooded the world with cheap steel.
- More US trading partners - including Germany, Australia, and Britain - voice strong opposition to the tariffs.
A real expert on national security, Defense Secretary Jim Mattis, has been decidedly cool on Ross' protectionist project and said so in a memorandum to the commerce secretary, albeit between the lines.
"Gary was here yesterday afternoon, I talked to him in my office several times, so I don't have any reason to think otherwise", White House spokeswoman Sarah Sanders told reporters. "Example, when we are down $100bn with a certain country and they get cute, don't trade any more, we win big".
Trump invoked national security as the rationale for imposing the tariffs, without making any distinction between friendly suppliers like Canada and potential adversaries like China or Russian Federation. Mr Trump has been criticised by a swath of senior lawmakers from his own Republican Party, but has won support from some Democratic legislators.
Mattis also urged making it clear to USA industry that protection would be conditional, "to set clear expectations domestically regarding competitiveness".
Howe's union, the United Steelworkers, is already lobbying the US government for changes, he says, and hopes American ownership in the Canadian steel industry will put Canada at an advantage.
Mr Ciobo has also raised concerns about potential retaliatory action by other major economies leading to a slowdown in economic growth.