Insurers say Saturday is too soon to meet the White House’s goals on rapid tests.

Starting Saturday, new federal rules will require private insurers to cover the at-home coronavirus tests that Americans buy in pharmacies and other stores. The new system could, in theory, allow millions of people to pick up tests at thousands of locations without spending any money.

The reality, at least in the short term, is likely to be messier: Some insurers say it will probably take weeks to fully set up the system the White House envisions.

The new process will be hard, the insurers say, because over-the-counter coronavirus tests are different from the doctor’s visits and hospital stays they typically cover.

The tests do not currently have the type of billing codes that insurers use to process claims. Health plans rarely process retail receipts; instead they’ve built systems for digital claims with preset formats and long-established billing codes.

Because of this, some insurers plan to manage the rapid test claims manually at the start.

“This is taking things back to the olden days, where you’ll have a person throwing all these paper slips in a shoe box, and eventually stuffing it into an envelope and sending it off to a health insurer to decipher,” said Ceci Connolly, the chief executive of the Alliance of Community Health Plans, which represents smaller, nonprofit insurers.