Workers at Kaiser Permanente — the nation’s largest health care nonprofit organization — began a strike Wednesday morning that is set to within hours see more than 75,000 union members walk out of hospitals and medical offices after the company and labor negotiators failed to resolve a dispute over staffing levels.

The Coalition of Kaiser Permanente Unions has described the work stoppage as the largest strike of health care workers in U.S. history.

The strike will target Kaiser hospitals and medical offices serving California, Colorado, Oregon, Virginia, the District of Columbia and Washington state.

The strike began at 6 a.m. ET in D.C. and Virginia.

Other workers will be scheduled to walk out at 6 a.m. local time in the remaining states.

The striking workers include vocational nurses, emergency department technicians, radiology technicians, X-ray technicians, respiratory therapists, medical assistants, pharmacists and hundreds of other positions.

Kaiser Permanente serves nearly 13 million patients and operates 39 hospitals and more than 600 medical offices across eight states and the District of Columbia.

Kaiser said it has contingency plans to ensure patients continue to receive care during a strike.

The strike by Kaiser Permanente employees is the latest action by organized labor this year as inflation and a workforce shortage have brought tensions over pay, benefits and staffing to a boiling point.