The Treasury Department is considering taking unprecedented control over key operations of the U.S. Postal Service by imposing tough terms on an emergency coronavirus loan from Congress, which would fulfill President Trump’s longtime goal of changing how the service does business, according to two people familiar with the matter.

Officials working under Treasury Secretary Steven Mnuchin, who must approve the $10 billion loan, have told senior officials at the USPS in recent weeks that he could use the loan as leverage to give the administration influence over how much the agency charges for delivering packages and how it manages its finances, according to the two people, who spoke on the condition of anonymity because the talks are preliminary.

Trump has railed for years against what he sees as mismanagement at the Postal Service, which he argues has been exploited by e-commerce sites such as Amazon, and has sought […]