(NewsNation)  — The U.S. Postal Service has temporarily stopped accepting inbound packages from China and Hong Kong, officials announced Tuesday, as President Trump’s 10% tariff on Chinese imports took effect.

Trump’s order to impose new taxes on Chinese goods coming into the United States ended duty-free handling of parcels, which had previously been considered “de minimis” shipments.

Letters and “flats” from China and Hong Kong will still make it through, the USPS said in a brief statement on its website.

Trump recently threatened tariffs against China, Mexico and Canada, three countries that he said were not doing enough to crack down on the production and distribution of deadly fentanyl. The U.S. and the latter two countries reached border-security agreements to pause the tariffs.

In retaliation, Chinese officials announced they were raising tariffs on certain U.S. goods coming into China.