US Senate Majority Leader Mitch McConnell has expressed concern that President Donald Trump's steel tariffs could spark a trade war, but the top Republican signaled that Congress was unlikely to nullify the tariffs through legislation

Washington (AFP) - The most powerful member of the US Senate said Tuesday it was “highly unlikely” that Congress would pass legislation nullifying the tariffs President Donald Trump announced on steel and aluminum imports.

Senate Majority Leader Mitch McConnell has previously joined House Speaker Paul Ryan and other Republican lawmakers in warning that the duties announced by Trump last week had the potential to spark an international trade war.

But McConnell appeared to pour cold water on the prospect of Congress blocking Trump’s move.

“The thought that the president would sign a bill that would undo actions he’s taken strikes me as remote at best,” he told reporters.

“I think it’s highly unlikely we’d be dealing with that in a legislative way,” he said.

McConnell added that there was still “a lot of concern” about the tariffs among Republicans, whose party has traditionally embraced free trade.

Senate Republican Jeff Flake, a frequent critic of the president, on Monday announced he was introducing legislation to nullify the tariffs.

“You can be pro-growth, you can be pro-tariff, but you can’t be both,” Flake said on the Senate floor, as he urged his colleagues to exercise their constitutional oversight role and “invalidate these irresponsible tariffs.”

Such a law would be guaranteed to face a presidential veto.

Overcoming a veto requires a two-thirds majority in both the Senate and House of Representatives, meaning the Republican majority would need significant support from the Democratic opposition.