Labor Secretary Marty Walsh, during a media blitz on Thursday, said that the new Biden administration rule that requires private employees to show proof of COVID-19 vaccination or get tested for COVID-19 on a regular basis is not a mandate.

“This isn’t a mandate—this is a vaccine or testing,” Walsh, a former mayor of Boston, said during an appearance on MSNBC.

“What we want to do is just encourage people to get vaccinated, if they choose not to get vaccinated, we’re asking—they’re going to get tested and then, in the workplace, when they’re around other people, they’re going to wear a mask. This is not a mandate,” he added on CNN.

The Labor Department’s Occupational Safety and Health Administration (OSHA) promulgated earlier in the day what’s known as the emergency temporary standard that outlines the requirements for private employers.

The requirement mandates businesses with 100 or more workers to either obtain proof of COVID-19 vaccination from each employee or results from COVID-19 testing done on a regular basis, at least once a week. It may be expanded to smaller businesses before being finalized.

Critics said the standard is clearly a mandate.

“This new rule is illegal and unconstitutional. It circumvents the normal legal process, along with Congress, to claim emergency powers to impose a mandate on American business,” Rick Esenberg, president and general counsel at the Wisconsin Institute for Law & Liberty, which is representing two businesses suing the administration over the standard, said in a statement.