Republicans loudly booed President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE’s announcement Thursday that he will impose steep tariffs on imported steel and aluminum.

GOP lawmakers joined business groups in declaring that slapping 25 percent tariffs on steel and 10 percent tariffs on aluminum will hurt consumers by raising prices and leading trading partners to retaliate against U.S. goods.

Opposition came from GOP leaders in the House and Senate, rising Republican stars and hardline conservatives.

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“The speaker is hoping the president will consider the unintended consequences of this idea and look at other approaches before moving forward,” Doug Andres, a spokesman for Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.), said in a statement.

Sen. John Thune John Randolph ThuneWhat Senate Republicans have said about election-year Supreme Court vacancies The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump contradicts CDC director on vaccine, masks MORE (S.D.), the No. 3 Republican in the Senate, also criticized the move.

“We have concerns, obviously, about actions taken that would create retaliatory action by some of our trading partners and our competitors out there, so I think, you know, we would like to see the White House adopt a, sort of, pro-free-trade position,” he said.

Conservative Sen. Ben Sasse (R-Neb.) said Trump was proposing “a massive tax increase on American families” and accused him of betraying GOP principles.

“Protectionism is weak, not strong. You'd expect a policy this bad from a leftist administration, not a supposedly Republican one,” he said.

Republicans in the last week had repeatedly urged Trump to not impose tariffs, arguing that doing so would destroy more jobs than they would save.

But their pleadings appeared to fall flat with Trump, who made trade a central part of his presidential campaign, arguing U.S. workers had lost out to pro-free-trade policies backed by Washington politicians in both parties.

“We're going to build our steel industry back and we're going to build our aluminum industry back,” Trump said Thursday.

A handful of Republicans, including some from manufacturing-heavy states in the Midwest, did express support for the Trump plan.

“I have argued that certain parts of our industry here do need immediate protection,” Sen. Rob Portman Robert (Rob) Jones PortmanMcConnell locks down key GOP votes in Supreme Court fight Romney undecided on authorizing subpoenas for GOP Obama-era probes Congress needs to prioritize government digital service delivery MORE (R-Ohio) said on Fox News.

Cleveland is home to steel manufacturer ArcelorMittal’s Cleveland Works plant, one of nine integrated steel mills operating in the U.S.

Trump also won some support from Democrats.

Sen. Sherrod Brown Sherrod Campbell BrownBipartisan praise pours in after Ginsburg's death Emboldened Democrats haggle over 2021 agenda Hillicon Valley: Russia 'amplifying' concerns around mail-in voting to undermine election | Facebook and Twitter take steps to limit Trump remarks on voting | Facebook to block political ads ahead of election MORE (D-Ohio) called for aggressive action.

“They’ve been talking about this and walked up to the edge for 10-and-a-half months now, causing more steel job losses, causing more U.S. companies hardship, lost revenues, lower sales, and look where we are,” he said.

Stocks fell on the news of Trump’s tariffs as businesses warned of a trade war and higher costs for imports. The Dow Jones industrial average fell more than 420 points on the day.

“The problem with any kind of tariff or tax hike on imports is that it doesn’t make America more competitive or punish high-tax countries, it only hurts American industries by driving up manufacturing costs and, ultimately, costing jobs,” said Nathan Nascimento, executive vice president of Freedom Partners, a right-leaning group partly funded by billionaire industrialists Charles and David Koch.

Sen. Lamar Alexander Andrew (Lamar) Lamar AlexanderMcConnell locks down key GOP votes in Supreme Court fight Alexander backs vote on Trump Supreme Court nominee: What Democrats 'would do if the shoe were on the other foot' Toobin: McConnell engaging in 'greatest act of hypocrisy in American political history' with Ginsburg replacement vote MORE (R-Tenn.) noted that when President George W. Bush imposed steel tariffs in 2002, higher steel prices led to net job losses.

Bush was forced to drop the tariffs within a year after trading partners retaliated.

“Targeted measures against countries that don’t play by the rules, such as China, could help American workers," Alexander said. “Broad tariffs against steel and aluminum imports will raise prices on consumers and hurt American workers.”

Trump’s decision, which could still change by next week, went slightly beyond the Commerce Department's recommendation of a 24 percent tariff on steel and a 7.7 percent tariff on aluminum.

Under section 232 of the trade law, the president can impose tariffs or quotas on imported materials for national security purposes.

“I generally support free trade, but there are instances where because of national security you’ve got to do things, and this may be one of them,” said Sen. John Kennedy John Neely KennedyMORE (R-La.), who said he was still undecided on the move ahead of the announcement.

Toomey said he didn’t buy the national security argument, and noted that the United States had already taken sensible trade action against Chinese steel dumping.

“Our defense needs are a tiny fraction of our domestic consumption of steel, so it’s not a plausible argument that we need it for national security,” he said.