President Trump announced Friday that hospitals will be reimbursed for treating uninsured covid-19 patients, using some of the $100 billion that Congress allotted last week to prop up health-care institutions straining financially because of the pandemic.

During a White House briefing, Health and Human Services Secretary Alex Azar provided the rough outlines of the plan, saying an unspecified “portion” of that $100 billion would be available to hospitals for the care of patients without health coverage. He said that hospitals will be paid the same rates as under Medicare, the federal insurance program for older Americans, and that hospitals will be forbidden to bill the patients for the difference between their usual charges and the federal rates.

Azar said the payments would be “fast, fair, simple and transparent.”

The administration decided against one method that could have blunted the effect of people losing health benefits when they lose a job. Officials resisted urging by health insurers and others to reopen the federal insurance exchange created by the Affordable Care Act for the roughly three dozen states relying on the HealthCare.gov online sign-up system. Azar noted Friday that the law gives people who lose job-based health benefits an automatic special enrollment period to buy ACA health plans.

In announcing the hospital payments, the president, Vice President Pence and Azar did not disclose critical details — such as how much of the $100 billion would be reserved for this purpose and how the money would be allocated. Hospital industry officials said immediately before the announcement that they have been unable to learn how this would work.