A divided U.S. appeals court ruled on Friday that most of Donald Trump'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 Trump administration a chance to file an appeal with the U.S. Supreme Court.

Trump has made tariffs a pillar of U.S. 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.