WASHINGTON – President Trump renewed his criticism of U.S. Postal Service policies this week, directing U.S. officials to get rid of international discounts that can make it cheaper to ship goods to a U.S. customer from China than from an American warehouse.

The decades-old discounts were established by a United Nations agency to help people in developing countries afford international mail. Now they mean a Chinese company often can ship a bike part or a T-shirt to a customer in Des Moines for a fraction of the cost paid by...