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WASHINGTON — Republicans on Capitol Hill reacted angrily to President Donald Trump's announcement Thursday that he is going forward with new tariffs on steel and aluminum, arguing that the move will harm the economy and that it threatens to start a broader trade war.

And while there are limits to what they can do to stop it, members are contemplating measures that could block the president from fully implementing his proposal.

"I don't think Republicans will put up with this, and I personally believe that we may be able to stop it in the Congress," Sen. Orrin Hatch, R-Utah, said.

The president announced a 10 percent tax on imported aluminum and a 25 percent tax on imported steel, carving out exceptions for imports from Canada and Mexico. But those exemptions weren't enough to placate congressional Republicans who have traditionally opposed protectionist action on trade.

GOP leaders had lobbied the White House from moving forward, writing letters, speaking out in the media and through outreach to the president and his advisers.

During a conference call between White House officials and GOP Hill staffers Thursday, administration representatives requested favorable comments from members on the president’s plan, a suggestion that the staff in one office laughed at, according to a Republican aide.

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In a rare rebuke of the president, Republicans are vowing to continue challenging him in ways that could result in either new legislation or support for expected legal challenges to the move.

"I disagree with this action and fear its unintended consequences," House Speaker Paul Ryan said. "There are unquestionably bad trade practices by nations like China, but the better approach is targeted enforcement against those practices."

Senate Majority Leader Mitch McConnell said the exemptions for Canada and Mexico are not enough.

"Members of the Senate, myself included, are concerned about the scope of the proposed tariffs on steel and aluminum and their impact on American citizens and businesses, including many I represent in Kentucky," McConnell said.

And Sen. Ben Sasse, R-Neb., said that the president's "bad ideas" will kill steel jobs.

"You have 140,000 steel production workers. Some of them will be mildly helped by the president’s tariffs. Far more jobs will be lost for other factory workers," Sasse said.

Republicans are exploring ways to blunt the president’s authority on an issue on which they disagree.

Congress has the authority to act on trade issues, but the pendulum has swung in recent years, through court cases and by Congress delegating its authority to the executive branch.

"The Constitution gives the responsibility to the Congress, and the Congress has consistently delegated these powers to the executive branch," Sasse said.

Sen. Jeff Flake, R-Ariz., introduced legislation that would nullify the tariffs.

"I urge my colleagues to pass it before this exercise in protectionism inflicts any more damage on the economy," Flake said in a statement.

And Sen. Mike Lee, R-Utah, has legislation that would attempt to rein in the president on trade by having trade action going through a congressional approval process. The president would have to submit a report to Congress before “raising any trade barriers.” And both bodies of Congress would have to pass a joint resolution approving any unilateral trade action.

"We'll continue to do oversight on this," Sen. Ron Johnson, R-Wisc., said.