WASHINGTON, Jan 7 (Reuters) - Conservative U.S. Supreme Court justices on Friday questioned the legality of President Joe Biden"s pandemic-related vaccine-or-testing mandate for large businesses but appeared more receptive to his administration"s vaccine requirement for healthcare facilities at a time of surging COVID-19 cases. The court"s nine justices, who are all vaccinated, heard more than 3-1/2 hours of arguments in two cases that test presidential powers to combat a raging public health crisis that already has killed roughly 835,000 Americans. The conservative justices, who hold a 6-3 majority, signaled sympathy toward arguments by the state of Ohio and a business group that the federal workplace safety agency that issued the rule affecting businesses with at least 100 workers - a policy requiring vaccines or weekly COVID-19 tests for more than 80 million employees - overstepped its legal authority. The challengers have asked the court to block the policy before the administration begins enforcement on Monday. The court"s conservatives suggested that the 1970 law that created the Occupational Safety and Health Administration (OSHA) did not authorize this type of broad emergency action. They seemed more open to a separate federal vaccine requirement that states led by Missouri and Louisiana are asking the court to block nationwide. It covers an estimated 10.3 million workers at about 76,000 healthcare facilities including hospitals and nursing homes that accept money from the Medicare and Medicaid government health insurance programs for elderly, disabled and low-income Americans. The conservative justices have shown skepticism toward sweeping actions by federal agencies in past rulings. Decisions in both cases are expected quickly. The arguments underscored how divisive the issue of vaccination has become in the United States, as in many nations. The three liberal justices indicated that both policies were justified during a pandemic showing no signs of abating, with an upswing in COVID-19 cases driven by the fast-spreading Omicron coronavirus variant. "This is a pandemic in which nearly a million people have died," liberal Justice Elena Kagan said, referring to the U.S. death toll during arguments over the OSHA mandate. "It is by far the greatest public health danger that this country has faced in the last century. More and more people are dying every day. More and more people are getting sick every day. ... And this is the policy that is most geared to stopping all this." Chief Justice John Roberts and fellow conservative Justices Neil Gorsuch and Brett Kavanaugh indicated that the OSHA rule could be invalid under a legal doctrine that says Congress must provide a clear statement on a specific issue in order for a federal agency to issue broad regulations on it. The conservative justices suggested Congress or individual states would be better suited to act. SPANISH FLU A general view of the U.S. Supreme Court building in Washington, U.S. October 13, 2021. REUTERS/Jonathan Ernst/File Photo REUTERS/Brendan McDermid A general view of the U.S. Supreme Court building in Washington, U.S. October 13, 2021. REUTERS/Jonathan Ernst/File Photo 1/2 REUTERS/Brendan McDermid Roberts voiced doubt that the law passed by Congress establishing OSHA empowered it to take such action. "That was 50 years ago that you"re saying Congress acted. I don"t think it had COVID in mind. That was almost closer to the Spanish flu than it is to today"s problem," Roberts said, referring to the pandemic that occurred a century ago. The White House has said the two temporary mandates will save lives and strengthen the U.S. economy by increasing the number of vaccinated Americans by the millions. "I would find it would be unbelievable to be in the public interest to stop these vaccinations," liberal Justice Stephen Breyer said. Some justices raised the possibility of the court issuing a temporary stay blocking the OSHA rule while the court decides how to proceed. Roberts and Kavanaugh appeared more sympathetic to the Biden administration"s arguments regarding the healthcare facilities mandate issued by the Centers for Medicare & Medicaid Services (CMS), the agency responsible for administering those programs. Kavanaugh noted that private healthcare providers did not challenge the mandate that states are contesting. Conservative Justice Amy Coney Barrett suggested the government could require vaccinations in certain facilities but not others. Gorsuch seemed skeptical of the policy as a whole, questioning whether CMS has the authority to issue a vaccine regulation because such action affects an employer"s staffing decisions, which Congress has said the agency could not do as part of its Medicaid and Medicare funding requirements. Gorsuch said that "you cannot use the money as a weapon to control these things." All the government is doing, Kagan said, is "to say to providers, you know what, basically, the one thing you can"t do is to kill your patients, so you have to get vaccinated." Liberal Justice Sonia Sotomayor participated in the arguments from her chambers. Ohio Solicitor General Benjamin Flowers and Louisiana Solicitor General Liz Murrill participated remotely by telephone. Flowers tested positive for COVID-19, his office said. Murrill"s office said she acted in accordance with the court"s COVID-19 protocols, which require lawyers to argue remotely if they receive a positive test. The justices spent much of the pandemic working remotely before returning to in-person arguments in October, although the building remains closed to the public. Biden"s administration asked the justices to lift lower court orders blocking the CMS mandate in half the 50 states. The Cincinnati-based 6th U.S. Circuit Court of Appeals on Dec. 17 lifted an injunction issued by another court that had blocked the OSHA rule, prompting challengers to ask the Supreme Court to intervene.