NEW YORK — A divided US appeals court ruled on Friday that most of the Donald Trump administration's tariffs are illegal, undercutting the Republican president's use of the levies as a key international economic policy tool.

The court allowed the tariffs to remain in place through Oct 14 to give the administration a chance to file an appeal with the Supreme Court.

The decision came as a legal fight over the independence of the Federal Reserve also seems bound for the Supreme Court, setting up an unprecedented legal showdown this year over Trump's entire economic policy.

Trump has made tariffs a pillar of US foreign policy in his second term, using them to exert political pressure and renegotiate trade deals with countries that export goods to the United States.

The tariffs have given the Trump administration leverage to extract economic concessions from trading partners but have also increased volatility in financial markets.

Trump lamented the decision by what he called a "highly partisan "court, posting on Truth Social, "If these tariffs ever went away, it would be a total disaster for the country."

He nonetheless predicted a reversal, saying he expected tariffs to benefit the country "with the help of the Supreme Court".

The 7-4 decision from the US Court of Appeals for the Federal Circuit in Washington, DC, addressed the legality of what Trump calls "reciprocal" tariffs imposed as part of his trade war in April, as well as a separate set of tariffs imposed in February against Canada, China and Mexico.

Democratic presidents appointed six judges in the majority and two judges who dissented, while Republican presidents appointed one judge in the majority and two dissenters.

The court's decision does not affect tariffs issued under other legal authority, such as the administration's tariffs on steel and aluminum imports.

Trump justified both sets of tariffs — as well as more recent levies — under the International Emergency Economic Powers Act, which gives the president the power to address "unusual and extraordinary" threats during national emergencies.

"The statute bestows significant authority on the President to undertake a number of actions in response to a declared national emergency, but none of these actions explicitly include the power to impose tariffs, duties, or the like, or the power to tax," the court said.

The Department of Justice has argued that the law allows tariffs under emergency provisions that authorize a president to "regulate "imports or block them completely.

Trump declared a national emergency in April over the fact that the US imports more than it exports, as the nation has done for decades. Trump said the persistent trade deficit was undermining US manufacturing capability and military readiness.

Agencies via Xinhua