Tens of thousands of healthcare workers in the United States walked off the job Wednesday, beginning one of the sector's largest strikes in recent history over what they say is a staffing shortage, as America's year of labor discontent rolled on.

The walkout of more than 75,000 workers at Kaiser Permanente, the country's largest non-profit health care organization, comes as surging inflation has spurred industrial action across the US, from Hollywood actors to Detroit autoworkers.

"Kaiser executives are refusing to listen to us and are bargaining in bad faith over the solutions we need to end the Kaiser short-staffing crisis," vocational nurse Jessica Cruz, who works at Kaiser Los Angeles Medical Center, said in a union statement.

"I see my patients' frustrations when I have to rush them and hurry on to my next patient. That's not the care I want to give.

"We're burning ourselves out trying to do the jobs of two or three people, and our patients suffer when they can't get the care they need due to Kaiser's short staffing."

Kaiser Permanente locations in Washington DC, Virginia, California, Colorado, Oregon and Washington state were expected to be affected by the three-day strike.

Kaiser said centers would remain open, but warned there would be "longer-than-usual" wait times.

A Kaiser spokesman told journalists on Tuesday that talks were continuing.

"Several agreements over specific provisions have been reached" with the Coalition of Kaiser Permanente Unions, he spokesman said, adding negotiators were prepared to meet around the clock "until we reach a fair and equitable agreement."

The union, which says this will be the largest healthcare worker strike in US history, is pushing for pay increases and protections against subcontracting and outsourcing of labor.

It has threatened to engage in further strike action in November "if Kaiser continues to commit unfair labor practices.

Inflationary pressures