Tensions between Chicago’s mayor and police over the city’s vaccine mandate grew this week as the head of the police union urged officers to ignore a deadline to report their vaccination status.

The head of the Chicago branch of the Fraternal Order of Police, John Catanzara, urged members of the union in a video message this week to “hold the line.”

Chicago city employees, including police officers, are required to report their vaccination status by Friday. Employees who aren’t vaccinated will be required to get tested twice weekly, a temporary measure until the end of the year as the city decides what to do with unvaccinated employees.

He told officers not to submit their vaccination statuses, and instead to flood the city with exemption requests on Thursday, the Washington Post reports.

Officers and other city employees who fail to report their vaccination status by Friday will “be placed in a non-disciplinary, no pay status,” according to Mayor Lori Lightfoot’s office.

Catanzara said that “it’s safe to say the city of Chicago will have a police force at 50 percent or less” over the weekend.