WASHINGTON — Congressional Republicans and business groups were bracing Wednesday for the impact of expected tariffs of 25 percent on imported steel and 10 percent on aluminum, appearing resigned to additional protectionist trade actions as President Donald Trump signaled economic battles with China.

The White House said Trump was expected to make a final announcement as early as today and officials were working to include language in the tariffs that would give Trump the flexibility to approve exemptions for certain countries. Mexico, Canada and other countries may be spared from planned steel and aluminum tariffs under national security “carve-outs,” the White House said Wednesday, describing a move that could soften the blow amid threats of retaliation by trading partners and dire economic warnings from lawmakers and business groups.

Press secretary Sarah Huckabee Sanders told reporters the exemptions would be made on a “case by case” and “country by country” basis, a reversal from the policy articulated by the White House just days ago that there would be no exemptions.

Treasury Secretary Steven Mnuchin said the administration was “definitely going to end up” with the across-the-board tariffs Trump is seeking — 25 percent on steel imports, 10 percent on aluminum. “But, again, there will be a mechanism where, to the extent that the president wants to give waivers, the president can do that,” Mnuchin told Fox Business.

The looming departure of White House economic adviser Gary Cohn, a former Goldman Sachs executive who has opposed the promised tariffs, set off anxiety among business leaders and investors worried about a potential trade war. “We urge you to reconsider the idea of broad tariffs to avoid unintended negative consequences to the U.S. economy and its workers,” 107 House Republicans wrote in a letter to Trump.

Lawmakers opposed to the tariffs, including House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell, have suggested more narrowly focused approaches to target Chinese imports. But members of Congress have few tools at their disposal to counter the president, who has vowed to fulfill his campaign pledge.

“I don't think the president is going to be easily deterred,” said Sen. John Cornyn, R-Texas, who has suggested hearings on the tariffs.

“He's already indicated a degree of flexibility, I think a very sensible, very balanced degree of flexibility,” Commerce Secretary Wilbur Ross told CNBC. “We're not trying to blow up the world.”

Trump signaled that other trade actions could be in the works. In a tweet, he said the “U.S. is acting swiftly on Intellectual Property theft.” A White House official said Trump was rreferring to an investigation of China in which the U.S. trade representative is studying whether Chinese intellectual property rules are “unreasonable or discriminatory” to American business.

The official, who spoke on the condition of anonymity to discuss internal deliberations, said an announcement on the findings of the report — and possible retaliatory actions — were expected within the next three weeks.

The EU’s trade commissioner, Cecilia Malmstroem, said Wednesday that the bloc is ready to retaliate with countermeasures, escalating the risk of a trade war of increasing taxes on traded goods. Many economists say such conflicts tend to hurt all sides because exporting producers suffer but so do consumers, who face higher costs.

Malmstroem said the EU is circulating among member states a list of U.S. goods to target with tariffs so that it can respond as quickly as possible. The list so far includes U.S. steel and agricultural products, as well as other products such as bourbon, peanut butter, cranberries and orange juice.

“This is basically a stupid process, the fact that we have to do this. But we have to do it,” EU Commission President Jean-Claude Juncker had said Friday. “We can also do stupid.”

Business leaders, meanwhile, continued to sound the alarm about the potential economic fallout from tariffs, with the president and CEO of the U.S. Chamber of Commerce raising the specter of a global trade war. That scenario, Tom Donohue said, would endanger the economic momentum from the GOP tax cuts and Trump's rollback of regulations. “We urge the administration to take this risk seriously,” Donohue said.

The president has said the tariffs are needed to reinforce lagging American steel and aluminum industries and protect national security. He has tried to use the tariffs as leverage in ongoing talks to revise the North American Free Trade Agreement, suggesting Canada and Mexico might be exempted from tariffs if they offer more favorable terms under NAFTA.

White House senior adviser Jared Kushner and staff from the State Department and National Security Council met Wednesday with Mexican President Enrique Pena Nieto and other top officials in Mexico City.

Kushner has been the designated point person for the United States' relationship with Mexico. But ties have become more complicated in recent weeks, given that the White House recently downgraded Kushner's security clearance, raising questions about how effective he might be in a meeting with a head of state or whether there are key issues he might not be informed about.

The White House is weighing contenders to succeed Cohn, and names circulating include Goldman Sachs executive Jim Donovan, Council of Economic Advisers Chairman Kevin Hassett, and trade adviser Peter Navarro, who promoted Trump’s tariff plan.