The specter of nursing strikes is looming on both coasts, as newly empowered nurses’ unions confront hospitals pressed to cut costs amid changes in health care financing.

In New York, over 6,000 registered nurses are poised to walk out of three of the city’s most prestigious hospitals before the year’s end, mainly over changes to their health benefits and what they say are strains in staffing. The hospitals — Mount Sinai, Montefiore Medical Center and St. Luke’s-Roosevelt Hospital Center — already are contracting for strike replacements at more than double normal wages.

In California, where 23,000 nurses represented by the California Nurses Association staged a one-day strike in September over similar issues, a new 24-hour walkout is set for Dec. 22 at eight hospitals in the San Francisco Bay Area and one in Long Beach. Potential strikes in New Jersey and Minnesota are being advertised on the Web site of HealthSource Global Staffing, one of the largest strike replacement agencies, which promises “cool locations and hot paychecks” for nurses willing to fill in during a walkout.

In New York, the union, the New York State Nurses’ Association, has not yet given the hospitals a 10-day strike warning, which the law requires, and last-minute settlements are still possible. But its battle with the hospitals reflects common themes across the country.

The nurses, who voted overwhelmingly to authorize a strike, say they are being disrespected by a corporate hospital culture that demands sacrifices from patients and those who provide their care, but pays executives millions of dollars. Management officials defend executive pay as the price of competition for top leadership, and accuse the nurses of refusing what many other American workers have accepted: paying a share of their health insurance premiums, along with higher co-payments, deductibles and prescription costs.

Though finances differ, all hospitals face cuts in Medicaid and Medicare and uncertainty over budgets under new payment models. Among other changes are new measures of quality: hospitals will lose money if too many patients are readmitted within 30 days, or if they score poorly on patient satisfaction surveys — two areas in which nurses play a crucial role.

For patients, the stakes are high, according to a recent study of 50 nurses’ strikes in New York State between 1984 and 2004. The study, for the National Bureau of Economic Research, found that patient mortality was 19.4 percent higher during a strike, or that there was about one extra death for every 280 patients admitted, and that they were 6.5 percent more likely to be readmitted within 30 days.