The administration will launch a website allowing individuals to request the rapid tests, those people said, speaking on the condition of anonymity to discuss private planning sessions. Officials aim to begin shipping the kits by mid-January.

Test manufacturers and distributors seeking to provide a share of the 500 million tests have submitted proposals to the government, and the Biden administration on Thursday evening awarded its first contract toward the purchase, said a person with knowledge of the testing plan. A formal announcement on the effort could come as soon as next week.

The Postal Service is negotiating with its four labor unions to extend the seasonal workforce — the roughly 40,000 people brought in each year to help the agency work through a glut of holiday packages. The agency moved 13.2 billion pieces of mail and parcels between Thanksgiving and New Year’s Eve.