WASHINGTON, Jan 4 (Reuters) - The Biden administration is finalizing contracts for 500 million rapid COVID-19 tests that it plans to distribute for free to Americans who request them, spokeswoman Jen Psaki said on Tuesday. The Omicron variant of the coronavirus has swiftly spread across the United States since its detection on Dec. 1, replacing Delta as the dominant strain and sparking a new wave of infections that pushed recorded daily cases near the 1 million mark on Monday. Psaki did not share details on how soon the tests will be available. The administration, she said, is in the process of finalizing the contracts and expects the first shipment from manufacturers to come soon. The website to be used to request the free tests will be up and running later this month, she added. "This is about making them free and accessible to the people who want them," Psaki said. President Joe Biden announced the free test initiative in December as the Omicron variant sent Americans scrambling to obtain tests. Tests have become hard to find in many areas, and long lines often form where they are available. The Omicron variant is estimated to account for over 95% of the coronavirus infections circulating in the United States as of Jan. 1, the U.S. Centers for Disease Control and Prevention (CDC) said on Tuesday. The fast-spreading variant was first detected in southern Africa and Hong Kong in November and has since swept through the globe at lightning speed, although signs that it may cause milder symptoms than previous variants have offered some relief.