A pay dispute between NSW nurses and the state government will ramp up when thousands of union members walk off the job at public hospitals in a day-long strike.

The stop-work action by nurses and midwives on Tuesday is expected to affect elective surgery and cause delays for some patients, while support for life-saving care will be maintained.

The action is part of a NSW Nurses and Midwives' Association push for a 15 per cent one-year pay hike for members, a demand Premier Chris Minns has said is unaffordable.

All NSW public sector workers, including nurses, have been offered a three-year 10.5 per cent pay increase factoring in a mandatory rise in superannuation payments.

The union's general secretary, Shaye Candish, said public-sector nurses and midwives would strike for 12.5 hours, starting at 7am.

"Major rallies will also be held in Kogarah, Corrimal, Newcastle, Parramatta, Coffs Harbour, Bathurst, Gosford and Albury, with additional local protests co-ordinated," she said in a statement.

"Nurses and midwives do not take industrial action lightly and continue advocating for better pay and staffing to ensure all communities receive the safe clinical care they deserve."

The union, which represents more than 77,000 workers, had "made a compelling case" for the pay rise but the government had "shown no willingness to provide a meaningful revised wage offer", Ms Candish said.

"We shouldn't have to consider increasing industrial action but the government has failed to put a better offer on the table, which leaves us no option," she said.

The escalation comes after the government reportedly missed a deadline to present a fresh pay offer to the union.

Health Minister Ryan Park said pay negotiations were continuing and he would always work with the union in good faith.

"Nothing is more important to me as minister for health than investing in our essential health workers," he said.

Contingencies would be put in place to minimise disruption to patient care, Mr Park added.

"The strike action proposed is serious and I'm concerned it's been taken," he said.

He called on the union to look at what the Labor government had already delivered for health staff, including axing the former coalition administration's wages cap.

The opposition has been contacted for comment.