The U.S. Postal Service has asked  OSHA for a temporary waiver from President Biden’s coronavirus vaccine mandate, setting up a showdown on pandemic safety measures between the president and one of the government’s largest agencies.

In a letter dated Jan. 4 to the Occupational Safety and Health Administration, Deputy Postmaster General Douglas A. Tulino wrote that requiring workers to be vaccinated against the coronavirus or present weekly negative tests would hurt the agency’s ability to deliver the mail and strain the nation’s supply chains.

A vaccine-or-test mandate, he wrote, “is likely to result in the loss of many employees – either by employees leaving or being disciplined.“

The Postal Service is seeking a 120-day extension to implement the rule, saying that would allow enough time to update its systems for record collection and bargain with its unions over the details.

“Given the significant challenges that our nation’s supply chains are already experiencing, we respectfully suggest that the nation cannot afford the additional potential substantial harm that would be engendered if the ability of the Postal Service to deliver mail and packages is significantly negatively impacted,” USPS wrote in its request to OSHA.

Postal management noted it is subject to Privacy Act and Freedom of Information Act laws that do not apply to large, private sector employers, and it therefore faces a larger burden to adapt its systems to collect and store employee records. Collecting records for its 650,000 employees is a “prodigious undertaking,” USPS said, and it may require the agency to purchase additional “technological infrastructure.”

The agency must negotiate the implementation details of the rule with its unions, the Postal Service said, and expects it can complete that during the 120-day pause.

In the meantime, USPS does not want to divert attention away from its front-line supervisors who are still in the midst of the agency’s peak season. The vaccine-or-test mandate is likely to result in the loss of “many employees,” USPS said, and the current moment presents problematic timing. If the Supreme Court upholds the rule, the Postal Service said it will accept the impacts of the rule and adjust to it accordingly.

“By virtue of being a massive, unique, and complex agency, it can be very difficult and time consuming to make even modest changes to policies and procedures that impact the working conditions of … employees,” USPS said. “This is especially true when the collection and use of medical information is involved.”

It added it is seeking to avoid disruption of its operations, given that it does not currently have sufficient resources for implementation.

“While the impact to our service could be devastating at any time of year,” USPS said, “requiring the Postal Service to absorb what could inevitably be a dramatic loss of employees at a time when the labor market is extremely tight and in the middle of the Postal Service’s peak season would have a potentially catastrophic impact on our ability to provide service to the American public when demand is at its highest.”

The Postal Service would implement the temporary variance at all postal facilities nationwide. “Because the Postal Service has over 30,000 facilities, it would not be practical to list specific addresses for each postal facility.”