A Trump administration order over the weekend added a 10 percent tariff to goods from China and closed the de minimis exception, a loophole that lets packages valued under $800 enter the US duty-free. The new rules appear to have quickly resulted in people being asked to pay additional charges on many more shipments from China.

China alleges that the tariffs are based on unfounded and false allegations, and are in excess of the U.S.’s bound rates in a tariff agreement from 1994.

China announced retaliatory tariffs on select American imports and an antitrust investigation into Google on Tuesday, just minutes after a sweeping levy on Chinese products imposed by U.S.