The Occupational Safety and Health Administration was already a strained agency before the president announced the new requirement.

President Joe Biden says his sweeping Covid-19 vaccination and testing mandate will boost the economy and save lives, but as businesses prepare for the new requirement, they’re wondering not only what will be in the regulation, but how it will be enforced.

The mandate, which will apply to organizations with at least 100 employees and cover an estimated 80 million workers, has already drawn threats of lawsuits from two dozen Republican attorneys general and prompted some people to vow to quit their jobs. But a greater challenge for the administration could lie within the agency tasked with ensuring compliance.

The Occupational Safety and Health Administration was already handling a broad mission prior to the new rule, which it is expected to issue in a matter of weeks. To stretch its resources, the agency typically prioritizes high-risk industries and targets repeat offenders, and it offers help, in addition to issuing fines, to businesses that are out of compliance.

But OSHA had only about 862 inspectors in early 2020, according to a Freedom of Information Act response from the agency obtained by NBC News, to carry out all of its regulatory enforcement duties — and that number has trended downward over the last several years. This year, despite new hires, the agency lost another 65 inspectors, according to data obtained from OSHA.