US President Donald Trump on Thursday announced the US withdrawal from the Universal Postal Union (UPU) as a retaliation against China and other foreign nations that “undermine the goal of unrestricted and undistorted competition in cross-border delivery services.”

The UPU, conceived in 1873 by the US and four other countries, acts as a regulatory body endorsed by the UN to control international postage rates and prevent interruptions in the process. All but three nations belong to the UPU, and the founding member’s withdrawal has startled the union. “The decision of the United States of America to withdraw from the UPU treaties is a serious one,” said Director General Pascal Clivaz, “but I believe, with the support of other members, we can resolve the matter amicably.”

In a press briefing, foreign ministry spokesman Lu Keng told the Associated Press that China “regrets” the decision to depart the Postal Union. “We will continue working with all sides to make our contributions to the development of global postal service,” he continued.

The International Chamber of Commerce (the world’s largest business organization) issued a statement supporting the measure, claiming that “all governments [must] engage constructively in the months ahead to agree on reforms to the relevant UPU instruments to provide a level playing-field for all businesses and enhance the security and integrity of the global postal delivery system.”