President Donald Trump has been known to exaggerate what he sees as China's unfair advantages in trade. But with his latest complaint, having to do with the seemingly trivial matter of global postal fees, Trump has highlighted an unfair imbalance that should be relatively easy to put right.

Arcane rules make it possible for a Chinese e-retailer to send a package across the Pacific to a customer in the U.S. at a cost lower than what an American competitor would spend to ship the same item to a neighboring state.

This is because existing trade rules allow poor nations to pay lower rates than wealthy ones. That makes sense. But, insensibly, the rules still place China, the world's second-largest economy, in the same category as Bosnia, Botswana, Cuba and other developing countries.

The U.S. should be able to solve the problem without withdrawing from the Universal Postal Union entirely. A better strategy would be for the White House to reach a fairer arrangement as part of its larger trade negotiations with China.

Trump may be misguided on much of his trade policy with China, but this is one issue in which his demands are justified and, with the right approach, within reach.

From an editorial on Bloomberg Opinion