The critics include members of his own Republican Party.
Refusing to spare friendly countries from the punishing tariffs could further inflame tensions created by Trump's sudden announcement on Thursday to protect American metal producers on national security grounds.
Earlier, he had blamed the US's "very stupid" trade deals for, according to him, an $800 billion annual trade deficit.
His announcement came only after an intense debate among his top aides.
"When costs of raw materials like steel and aluminum are artificially driven up, all Americans ultimately foot the bill in the form of higher prices for everything from canned goods to electronics and automobiles", he added. He announced plans to set tariffs of 25 percent on imported steel and 10 percent on aluminum imports next week. He said the tariffs would be in effect for a long period of time.
Meanwhile, our trading partners are lining up, itching to retaliate. European Commission chief Jean-Claude Juncker vowed the bloc "will react firmly" to defend its interests. "Big trade imbalance!" Trump tweeted on Saturday.
China on Friday expressed "grave concern" about the matter.
"It's troubling to see an American administration revert to some of the failed policies of the past that not just discourages growth, but punishes [it]", Scheer said.
"The general consensus of the president was tariffs had to imposed, and they should be across the board without country exemptions", Navarro told CNN's Jake Tapper.
Canada buys more American steel than any other country, accounting for 50 per cent of USA exports, according to the Canadian Steel Producers Association.
They are scrambling to convince the President that he would spark a trade war that could stall the economy's recent gains if he does not reverse course.
Ross likewise downplayed the risk of retaliation, saying any trading partners who made a decision to cut United States imports in other areas would both raise their own costs and create openings for U.S. exporters.
Eisenberger and the mayor of Sault Ste Marie are talking about an alliance of steel-producing cities here and in the U.S.
French Economy Minister Bruno Le Maire on Friday warned the United States against a trade war with the European Union, saying there would "only be losers" in such a standoff. "What saves one job can jeopardize another".
Trudeau stressed in his comments he was prepared to "defend Canadian industry" and that the tariffs would also hurt US consumers and businesses because prices could rise.
Mr Ciobo was confident Australia's anti-dumping laws would prevent cheap foreign steel that would usually go to the U.S. from flooding the local market.