By Jeff Mason

WASHINGTON (Reuters) -President Joe Biden said on Thursday he is directing the U.S. government to procure an additional 500 million COVID-19 tests to help meet demand across the country amid the spread of the Omicron variant.

The order comes on top of another 500 million tests that the White House pledged before the Christmas holiday would be available to Americans this month.

"Today I'm directing my team to procure ... an additional 500 million more tests to distribute for free," Biden said ahead of a briefing from advisers.

Reuters was first to report Biden's move.

The president has come under criticism https://www.reuters.com/article/us-health-coronavirus-biden-analysis-idCAKBN2IZ0WD for not focusing more on testing earlier as part of his strategy for fighting the pandemic. A nationwide shortage of tests has plagued the response in recent weeks during the rampant spread of the highly contagious Omicron variant.

A White House official said earlier on Thursday the tests would be free for American consumers and that the White House would share more details about their distribution at a later date. Details about the website that will have information on the first tranche of 500 million tests will be available on Friday, the official said.

When the original 500 million tests were announced, experts https://www.reuters.com/business/healthcare-pharmaceuticals/biden-omicron-measures-too-little-too-late-fast-moving-virus-experts-2021-12-23said the White House's actions were too slow and not bold enough to deal with Omicron's spread. Since then, the Department of Defense has signed contracts with two procurement companies, Revival Health https://www.reuters.com/world/us/pentagon-awards-contract-revival-health-covid-test-kits-2022-01-07 and Goldbelt Security https://www.reuters.com/world/us/pentagon-awards-52-mln-contract-covid-19-test-kits-2022-01-07, to provide them.

Tests have been difficult for many Americans https://www.reuters.com/world/us/americans-grapple-with-prolonged-testing-woes-amid-omicron-surge-2022-01-12 to find, driven in part by rapid test supply shortages as well as staffing shortages at the urgent care centers, pop-up sites and pharmacies that administer the tests. More recently, staffing at the laboratories that process the more complex PCR tests has also become a factor, frustrating many seeking to know quickly whether they are infected with COVID-19.

Biden acknowledged Americans' frustration but said testing availability had improved.

"This month it's estimated that we will hit approximately 15 million tests a day and we'll have over 375 million at-home rapid tests in January alone," he said. "That's a huge leap."

Biden said the administration was on track to roll out a website next week from which people will be able to order free tests to be shipped to their homes. He also said the administration would announce next week how it would make masks available to Americans for free.

While the official count of Omicron cases in the United States continues to rise, there are signs that in some areas that were hit early on, such as the Northeast, the pace of new infections has begun to slow.

(Reporting by Jeff Mason; additional reporting by Steve HollandEditing by Chizu Nomiyama, Heather Timmons and Jonathan Oatis)