GENEVA — The Trump administration is threatening to pull the United States out of the 145-year-old Universal Postal Union, saying some postal carriers like China’s aren’t paying enough to have foreign shipments delivered to U.S. recipients. A showdown looms at a special UPU congress that is being held Tuesday to Thursday in Geneva.

The complaint centers on the reimbursement that the U.S. Postal Service receives for providing final deliveries of bulky letters and small parcels sent from abroad — usually ones not weighing more than about 4½ pounds. Such mail can include high-value items like mobile phones, memory sticks or pharmaceuticals.

“Whatever happens, prices to ship via the postal network ... It’s going to cost more,” said Kate Muth, executive director of the International Mailers Advisory Group, which counts companies like eBay, DHL, Amazon, USPS or their affiliates as members. “The rates are going to go up.”

One of the few companies to chime in publicly has been eBay, whose grassroots network has warned of possible “service disruptions and dramatically increased costs for shipping through the US Postal Service” if the United States pulls out.

The administration complains that China and many other countries get to pay lower reimbursements because they’re classified as developing countries, putting U.S. companies at a disadvantage. It wants postal services like USPS to set their own rates — and right away, not months from now.

“Today, manufacturers in countries as small as Cambodia and as large as China pay less to send small parcels from their countries to New York than U.S. manufacturers do to ship packages from Los Angeles to the Big Apple,” Trump trade adviser Peter Navarro wrote in the Financial Times on Sept. 11. He said other countries like Canada, Norway and Brazil are also losing money from the UPU’s “distorted system.”