WASHINGTON (Reuters) — President Joe Biden signed an order on Wednesday requiring masks and physical distancing in all federal buildings and the development of a testing program for federal employees for COVID-19, in a first step to combat a pandemic that has claimed the lives of more than 400,000 Americans.

Biden’s order, the first one he signed at the White House hours after taking office, says federal employees, contractors and others in federal buildings or on federal lands should “wear masks, maintain physical distance, and adhere to other public health measures, as provided in (Centers for Disease Control and Prevention (CDC) guidelines.”

Biden directed agencies to “immediately take action…to require compliance with CDC guidelines” and for employees to wear masks and engage in social distancing.

In October, Biden vowed to require masks on airplanes and on interstate transportation, but he did not take that action on Wednesday. The transportation order is expected Thursday, officials said.

U.S. airlines, which have been requiring masks without a legal requirement for months, support Biden’s planned mandate.

Biden’s order Wednesday directs the CDC to “promptly develop … a testing plan for the federal workforce,” adding it will be “based on community transmission metrics and address the populations to be tested, testing types (and) frequency of testing, positive case protocols.

Biden said agencies may make exceptions to mask requirements, but must “require appropriate alternative safeguards.”

The Biden administration must implement new testing requirements for nearly all international air passengers that begin Tuesday, following a CDC order last week. Under the new rules, all U.S.-bound passengers age 2 and over must get negative COVID-19 test results within three calendar days of travel.

The Biden administration announced it would reimpose entry bans on most non-U.S. citizens who have recently been in Brazil, the United Kingdom, Ireland and most of continental Europe after President Donald Trump, in one of his last acts in office, issued an order Monday lifting them effective the same day the new testing rules take effect.

Biden spokeswoman Jen Psaki said Monday that the new administration planned “to strengthen public health measures around international travel in order to further mitigate the spread of COVID-19.”

Reporting by David Shepardson Editing by Chizu Nomiyama and Leslie Adler