President Joe Biden said on Thursday that more US firms should require COVID-19 vaccinations for their employees, calling the action critical to ending the pandemic and supporting the economy.

"Today I'm calling on more employers to act," Biden said.

"My message is: Require your employees to get vaccinated. With vaccinations, we're going to beat this pandemic finally. Without them, we face endless months of chaos in our hospitals, damage to our economy and anxiety in our schools."

Biden issued an order last month requiring all government employees and contractors to be vaccinated, as well as private firms with 100 or more employees to compel staff to be vaccinated by Dec. 8 or be checked for the coronavirus on a weekly basis. This edict applies to 100 million people, or almost two-thirds of the workforce.

On Thursday, the president stepped up his request for a visit to the site of a proposed Microsoft Corp data centre near Chicago. Clayco, a construction company, has stated that it intends to implement vaccine or testing requirements for all employees.

Biden highlighted other vaccination success stories, such as Chicago-based United Airlines, which became the first US carrier to set an October deadline for all employees to be fully vaccinated.

Biden praised other airlines and organisations that had followed suit, including Walt Disney Co, Walgreens Boots Alliance, and Microsoft.

Immunization requirements have broad public support, and Wall Street economists agree higher vaccination rates will stoke economic growth and add jobs, the Democratic president said.