President Trump argued Friday morning that the U.S. Postal Service is undercharging online retailers, such as Amazon, to deliver packages, amounting in the retailers gaining wealth while the postal service becomes “dumber and poorer.”

“Why is the United States Post Office, which is losing many billions of dollars a year, while charging Amazon and others so little to deliver their packages, making Amazon richer and the Post Office dumber and poorer? Should be charging MUCH MORE!” Trump tweeted.