WASHINGTON — Fulfilling a campaign promise, President Joe Biden plans to reopen the HealthCare.gov insurance markets for a special sign-up opportunity geared to people needing coverage in the coronavirus pandemic.

Biden is expected to sign an executive order Thursday, according to two people familiar with the plan, whose details were still being finalized. They spoke on the condition of anonymity because they were not authorized to discuss the pending order ahead of a formal announcement.

Although the number of uninsured Americans has grown because of job losses due to the economic hit of COVID-19, the Trump administration resisted calls to authorize a “special enrollment period” for people uninsured in the pandemic.

The White House had no comment on Biden’s expected order, but the two people familiar with the plan said the new enrollment period would not go into effect immediately. Instead, the White House wants to provide time for the Department of Health and Human Services to mount a marketing campaign, and for insurers to get ready for an influx of new customers.

The Obama-era health care law covers more than 23 million people through a mix of subsidized private insurance sold in all states, and expanded Medicaid adopted by 38 states, with Southern states being the major exception. Coverage is available to people who don’t have job-based health insurance, with the Medicaid expansion geared to those with low incomes.

Biden’s order would directly affect HealthCare.gov, the federal insurance marketplace currently serving 36 states. The marketplace concluded a successful annual sign-up season in December, with enrollment for 2021 growing by about 7%. Final numbers for this year that include insurance markets directly run by the states will be available soon.

Opening the insurance markets is also likely to result in higher Medicaid enrollment, since people who qualify for that program are automatically referred.

The special sign-up opportunity is only a down payment on health insurance for Biden, who has promised to build on former President Barack Obama’s health law to push the U.S. toward coverage for all. For that he’d need congressional approval.