The Biden administration on Thursday asked the Supreme Court to uphold its vaccine-or-testing mandate for large U.S. companies, as several business groups and GOP-led states seek to block the rule.

“The nation is facing an unprecedented pandemic that is sickening and killing thousands of workers around the country, and any further delay in the implementation of the [rule] will result in unnecessary illness, hospitalizations, and deaths because of workplace exposure to [Covid],” Solicitor General Elizabeth Prelogar said in the filing.

Earlier this month, a federal appeals court reinstated the administration's Covid vaccination policy for large private businesses after an earlier court ruling halted one of President Joe Biden’s key measures to increase vaccination numbers.

Biden announced the policy in September, stating that businesses with 100 or more employees must ensure their workforces are fully vaccinated, or require workers who aren't vaccinated to wear masks and show negative Covid test results at least once a week. Employers can face fines for not complying.

Several GOP-led states and business groups are involved in a lawsuit challenging the rule, arguing that it exposes companies to financial risk for refusing to comply and threatens their workforces.

In a 2-1 ruling, a panel for the Ohio-based 6th Circuit said the Occupational Safety and Health Administration workplace order for businesses with at least 100 employees was valid.

Prelogar argued in the filing that OSHA has the power to implement the rule through existing law after business groups and some states asserted that the agency lacks the authority.

"The OSH Act unambiguously grants OSHA the authority to promulgate emergency temporary standards without any exception for standards that might have large economic or political significance, and the issuance of the [rule] does not conflict with any other statutory provision," she said in the court filing.

"Congress, moreover, has specifically directed OSHA to use its existing regulatory authorities 'to carry out COVID-19 related worker protection activities' and has appropriated funds designated for OSHA to address workplace exposure to COVID-19," Prelogar said.

OSHA has said that it would not issue citations tied to its Covid vaccination mandate before Jan. 10, so that companies have time to implement the requirements. The federal agency also said there would be no citations related to its testing requirements before Feb. 9. The mandate was previously slated to take effect Jan. 4.

The Supreme Court is scheduled to hear oral arguments on challenges to the vaccination and mask requirements for large companies on Jan. 7. /NBC