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... The Trump administration imposed an additional 10% tariff on Chinese goods that came into effect on Tuesday and moved to close the "de minimis" exemption that allows importers and U.S. shoppers to avoid paying tariffs for packages worth less than $800.

The extra tariff and the elimination of de minimis follow repeated warnings by Trump that Beijing was not doing enough to halt the flow of fentanyl, a dangerous synthetic opioid, into the U.S.

Reuters reported previously that Chinese suppliers use the duty-free provision to export chemical materials for fentanyl by disguising them as gadgets and other low-cost goods.

USPS said the change will not impact the flow of letters and 'flats' - mail that can be up to 15 inches (38 cm) long or 3/4 inches (1.9 cm) thick - from China and Hong Kong. It did not immediately comment on whether this was tied to Trump's change to ending de minimis shipments from China and other countries. ...