The pay offer rejected by nurses this morning was the best the Government could offer, acting Prime Minister Winston Peters said.

Meanwhile, District Health Boards are vowing to do everything they can to avoid the strike in two days' time.

"This is the best we can do," Peters said of the latest pay offer. "We are saying give us some time.

But there was still time to avert industrial action, he said.

"We are still hoping .... reconciliation can happen."

Peters said the Government was very disappointed nurses had rejected the pay offer and had voted to strike.

Peters reiterated that not everything could be fixed in one year and nurses needed to be patient.

Peters said although the Government had a surplus, there were other issues such as the mycoplasma bovis outbreak and the PSA industrial action that prevented the Government from dipping into it for nurses.

He couldn't promise there would be money in next year's Budget that could be promised to nurses now.

However, he was confident the professionalism of nurses would ensure patient safety would not be at risk during Thursday's strike.

Nurses had given a commitment that lives would not be at risk during Thursday's strike, he said.

"That's what they've told us, that's what we trust they'll do."

Peters said he was not concerned about a perception of "winter of discontent" because of the amount of industrial action underway or planned.

Peters said nurses did not have to go on strike but would not go as far as to say any should cross the picket line on Thursday.

Thousands of nurses voted to walk off the job for the first time in 30 years on Thursday after rejecting the DHBs' latest pay offer.

The New Zealand Nurses' Organisation (NZNO) said members voted to reject the latest proposed District Health Board Nursing and Midwifery Multi-Employer Collective Agreement offer.

The decision means a 24 hour strike planned for Thursday will go ahead.

The latest pay offer was the fourth from DHBs, and the NZ Nurses Organisation noted voter turnout was high, and the result closer than last time.

DHB spokeswoman Helen Mason said they were disappointed nurses rejected the revised offer, and now their primary concern was ensuring patient and staff safety.

"We have already asked the Employment Relations Authority to help find a way forward.

"We respect nurses right to strike in support of their claims, we also need to recognise that negotiation involves a degree of compromise – we have moved significantly over the last six months and have made an excellent offer.

Mason said hospitals around the country were very busy at this time of year, and had already experienced significant disruption in the lead up to the strike.

"It is still not too late to prevent this disruption and we urge the NZNO and its members to help us try and find a war forward."

Mason said emergency and essential services would still be provided through the strike, and people should not delay seeking medical and hospital treatment if the matter was urgent.

NZNO Industrial services manager Cee Payne said 30,000 members would be involved in the strike, although some would work to ensure life preserving services continued.

"Life preserving services and contingency plans are coming to completion with the 20 district health boards.

"We are confident that these will be in place as patient safety and public safety is paramount."

DHBs have requested further facilitation, but NZNO responded that because there were no more funds for an improved offer, facilitation wouldn't be appropriate.

However the Employment Relations Authority had ordered that the organisation must continue with facilitation starting after lunch today and continuing tomorrow morning if need be.

She said it was unlikely the latest round of facilitation would result in an agreement nurses would be happy with if there was no more money available.

"The issues faced and reported by our members have arisen from a decade of severe underfunding of our public hospitals which have failed to keep pace with growing community need, the ageing population and workforce, and increased costs," Payne said.

She said some members were swayed by the promise of pay equity and some changes in pay for different nursing positions.

"But on the other side there was the issue of trust in DHBs delivering what they say, [nurses] want things legally spelled out in the agreement now.

"Their experience over the last ten years is DHBs haven't delivered on what they're saying around things like safe staffing."

NZNO chief executive Memo Musa admitted the situation was unprecedented, but said public safety would be "paramount".

"It is winter, this is a time when DHBs are traditionally under pressure.

"But it is the employers' responsibility to scale down services to a point where there are life-preserving services in place.

"Yes, this is unprecedented, but our commitment is to ensure that there are life-preserving services and emergency management protocols in place.

"I sympathise with those whose surgeries have been postponed, and appointments cancelled. It has not been an easy decision for nurses."

There are potentially over 30,000 NZNO members involved. Many staff covered by the DHB MECA have agreed to provide life preserving services over the duration of the strike.

National's health spokesman Michael Woodhouse said the strike was the result of the Government raising expectations when it was in opposition.

"The elective surgeries that have been and are being cancelled in preparation for the strike include cardiac surgery, surgeries for cancer and joint replacements," he said.

Woodhouse said the cancellation would have a significant impact on patients and their families who would have made arrangements, taken time off work and emotionally prepared for their scheduled surgery.

"It's clear that nurses were unhappy with the Government simply shifting the deck chairs on the original offer and they have now decided to push for more Government money," he said.

"The nurses were also frustrated that the Government entered the facilitation process saying 'that's all the money there is' and this is the effect of it. This move did not reflect good faith bargaining and it is now unclear how the situation will be resolved."

Woodhouse said because the Government restricted the facilitation process it was now likely to be unavailable to aid in resolving the negotiations.

The latest offer saw nurses given at least a 9.5 per cent pay rise over the next year while $38 million of new funding was offered to allow district health boards to hire extra staff.

Contingency planning for strikes continued while the votes were being cast, to ensure life preserving services continued if the offer was rejected.

That means many non-essential services, including surgeries and appointments, have already been cancelled throughout the country.

NZNO members previously voted to reject the DHBs' earlier offer of 9 per cent for all member nurses by August 2019, which equated to $500m.

Kapiti and Coast chief medical officer John Tait, speaking on behalf of clinicians around the country, said between 6,000 and 8,000 elective procedures would be deferred.

"Nurses are the cornerstone of hospital services. We cannot underestimate the impact of this strike.

"DHBs have been planning for a considerable length of time to reduce patients and patient demand, leading up to this strike.

"We will be, and are, working extremely hard to get people the care they need in acute emergency care. But in situations that are not life-threatening, care will take longer.

"Nurses are highly skilled professionals, and their skills cannot be replaced."