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President Donald Trump on Friday defended his controversial plan to slap huge tariffs on imported steel and aluminum amid intense GOP criticism and a growing global backlash, saying "trade wars are good, and easy to win" as international markets braced for more losses.

“When a country (USA) is losing many billions of dollars on trade with virtually every country it does business with, trade wars are good, and easy to win,” Trump tweeted early Friday. “Example, when we are down $100 billion with a certain country and they get cute, don’t trade anymore — we win big. It’s easy!”

A short time later, he returned to add, “We must protect our country and our workers.”

“Our steel industry is in bad shape. IF YOU DON’T HAVE STEEL, YOU DON’T HAVE A COUNTRY!” he said.

Trump’s morning tweets were in reference to his announcement Thursday that the U.S. would levy tariffs of 25 percent on imported steel and 10 percent on imported aluminum — a move that prompted fierce criticism from Republicans in Congress and dire warnings of retaliation from the country's trading partners, as well as led markets to tank.

Key players on Capitol Hill, including House Speaker Paul Ryan, R-Wis., and Sen. Orrin Hatch, R-Utah, the Senate Finance Committee chairman, were not given any heads up about Trump’s tariff announcement, and many broke ranks with Trump in an unprecedented way, with one after another coming forward during the day to caution about the dangers of tariffs and plead with Trump to hold off on any action.

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Sen. Ben Sasse, R-Neb., slammed Trump's concept of a "good" trade war in a statement Friday, and said fighting one would only lead to "so much losing."

"Trade wars are never won. Trade wars are lost by both sides. Kooky 18th century protectionism will jack up prices on American families — and will prompt retaliation from other countries," Sasse said. "Make no mistake: If the president goes through with this, it will kill American jobs — that's what every trade war ultimately does. So much losing."

Canada, a close U.S. ally and large trading partner, said Thursday that it viewed "any trade restrictions on Canadian steel and aluminum as absolutely unacceptable." The nation’s minister of foreign affairs warned that her country could “take responsive measures to defend its trade interests and workers."

The prospects of a trade war pushed the Dow down over 400 points at the close of trading on Thursday — and the decline continued into Friday’s session. The Dow Jones Industrial Average fell by more than 300 points, or 1.2 percent, in morning trading, before rallying to end the day down 0.3 percent. The S&P 500 and Nasdaq Composite indexes both closed the day in positive territory after suffering losses earlier.

Trump's decision, however, earned praise from at least one corner.

U.S. Commerce Secretary Wilbur Ross, who has been a proponent of tariffs and helped engineer the meeting that led to Trump's surprise announcement on the actions, told CNBC that the controversy surrounding the tariffs was just "hysteria" and "a lot to do about nothing."

In an unusual interview with the network that involved props, Ross, holding up at one point a can of Campbell's Soup and at another point a can of Coca-Cola, claimed that the potential price increases on consumer products that could result from the steel and aluminum tariffs would be "no big deal."

"Well I just bought this can today at a 7-Eleven down here, and the price was $1.99, so who in the world is going to be too bothered by six-tenths of a cent?" he said, holding up the Campbell's can.

Meanwhile, White House Press Secretary Sarah Huckabee Sanders, in brief comments to reporters Friday morning, acknowledged that some details still "needed to be finalized" on the plan, but said Trump remained "pretty committed" to his announcement.

When asked about Trump's supporting the idea of a trade war on Twitter, Sanders replied that the "president is still focused on long-term economic fundamentals" and "incredibly focused on the American worker and feels like both the steel and aluminum industry are both the backbone of this country."

She also dismissed reports that Gary Cohn, the White House’s top economic adviser, could leave his position in protest of the administration's tariff plan.

“I don’t have any reason to think otherwise right now,” she said, when asked whether Cohn would leave.