(NEXSTAR) – As the omicron variant sweeps through the U.S., becoming the most dominant strain of COVID-19 ahead of the holidays, the demand for testing has risen. President Joe Biden is expected to announce new actions to expand access to COVID testing, but for some retailers, it may be too late.

Tuesday morning, ahead of Biden’s announcement, Walgreens imposed a purchase limit on at-home COVID-19 testing products across its stores and online. Customers will now be limited to just four items per purchase “in an effort to help improve inventory.”

A short time later, CVS announced its own purchase limit. In a statement shared with Nexstar, the retailer says it continues to work to provide its stores with five at-home COVID tests but will also be imposing a purchase limit.

“To ensure equitable access to tests both in store and digitally, we’ve added a limit of six test kits per purchase. Due to a recent surge in demand, and to retain community-based access to tests in our stores, there may be temporary out-of-stocks for these products on CVS.com,” the statement continues. “We’re committed to providing families with protection and peace of mind during the holiday season, and we continue to offer access to lab-based testing with results available in 1-2 days or rapid COVID-19 testing at more than 4,800 CVS Pharmacy locations.”

A Walmart spokesperson says they are also seeing an “extremely high demand on Covid-19 at home testing kits.” While inventory levels at its stores are “strong,” inventory is limited for its online division. Customers are limited to eight testing kits per online order. Additionally, each store may set its own limits based on local inventory.

Statements regarding their own at-home COVID test supplies from Target and Kroger were not available at the time of publication. At-home COVID test kit manufacturers Abbott BinaxNOW and QuickVue did not immediately respond to Nexstar’s request for comment.

On Tuesday, Biden is expected to announce that his administration will purchase 500 million at-home COVID tests that will be free for any American who wants them. These testing kits will be available starting in January. The White House says Biden will also announce the continued use of the Defense Production Act to ensure the U.S. is producing COVID tests as quickly as possible and new federal testing sites nationwide.

Currently, the U.S. can conduct about 600 million tests per month, with home tests accounting for about half, according to researchers from Arizona State University.

The Associated Press contributed to this report.