WASHINGTON (AFP) - The rebellion is swelling among members of the US Congress' Republican majority dismayed over Donald Trump's contentious new trade tariffs, with many elected officials threatening to block the President's decree.
The US leader has triggered howls of protest in his own camp by slapping tariffs of 25 per cent on imports of steel and 10 per cent on aluminium on Thursday (March 8), with only Canada and Mexico exempt for the time being.
Historically proponents of free trade, several Republicans dubbed the measures "stupid" and "misguided" - if the United States increases the cost of both materials, they hold, American producers of vehicles and other products will suffer setbacks on the international playing field, and consumers will pay more.
Trump moreover found little support among Democrats, even though that party is historically more protectionist.
In the Senate, Republicans are opposing the duties en masse, with Senator Jeff Flake already preparing a Bill to "nullify these tariffs." His colleague Mike Lee, of the ultra-conservative Tea Party, immediately claimed congressional powers as defined in the Constitution's first article - which says the power to tax belongs to the legislature - promising "to make sure these tax hikes are never enforced."
And with midterm elections looming, the extraordinary backlash from the president's Republican Party sets up a showdown between the chief executive and his own majority lawmakers.
Just a few months after he helped drive Trump's landmark tax reform through Congress, Orrin Hatch, chairman of the Senate Finance Committee, expressed astonishment at the President's decision.
"I think there's a good chance that we will nullify the tariffs," he told reporters.
"I generally support the president on just about everything, but I think he's been misled, there are some people down there who have been misleading him on some of these things," Hatch continued.
"I'm disappointed because we just passed a tax bill and this kind of flies in the face of that. It's something I'm very upset about."
Congress now has several options: it could pass a law taking back from Trump powers regarding commercial matters, which have been doled out to the White House progressively since the 1930s for purposes of efficiency.
In the case of these tariffs, the Republican leader used a 1962 law authorising the President to tax certain imports in the name of national security protection - legislation rarely invoked in the past except in the notable case of oil.
Many Republicans hold that imposing tariffs on steel and aluminium are an abuse of this law and are pushing to restrict it.
Another law grants extensive powers to the president to negotiate trade agreements, allowing some 15 accords to be struck since 1979.
The latest version of this law, adopted under Barack Obama in 2015, will expire in July of this year unless Trump requests an extension until 2021.
Even then, Congress will have the opportunity to oppose the extension by passing a resolution of disapproval.
As Trump vows to sign new bilateral treaties and amend the North American Free Trade Agreement, congressional leaders could seize the moment to reaffirm their role in US trade policy.
For now, the top leadership has voiced a preference to collaborate with the administration to adjust and reduce the tariffs as much as possible, holding off on announcing a law.
Whatever Washington lawmakers opt to do, they will have to reach a two-thirds majority vote to overcome a presidential veto - forcing Republicans to find support among the Democratic opposition, a challenge in its own right.