WASHINGTON — The Biden administration on Monday argued that the federal government had all the power it needed to require large employers to mandate vaccination of their workers against the Covid-19 virus — or to require those who refuse the shots to wear masks and submit to weekly testing.

In a 28-page filing before the United States Court of Appeals for the Fifth Circuit, which temporarily blocked the mandate with a nationwide stay last week, the Justice Department argued that the rule was necessary to protect workers from the pandemic and was well grounded in law.