Hawke's Bay DHB chief executive Kevin Snee said that the DHB was now actively planning to reduce demand on services by rescheduling all non-urgent hospital services in preparation for industrial action.
The DHB was working with the NZNO to ensure emergency and life preserving services were available, if industrial action went ahead, he said.
"Nurses, midwives and healthcare assistants are a highly respected and valued part of the modern team-based approach to health services, and we are very concerned about the possibility of industrial action."
Affected patients would be contacted if there were going to be any changes to services.
The main priority for the DHB would be maintaining patient safety, and it would be working hard to make sure emergency and life preserving services were available if industrial action went ahead, he said.
In the meantime, DHBs were working to find a way to prevent industrial action.
DHB spokesperson Helen Mason said the offer that had been made was about much more than pay rates.
"The offer includes a commitment to an additional 500 nurses to address workforce demands. It also includes funding to ensure the implementation of the safe staffing programme.
"In total, the offer would invest more than half a billion dollars in more staff and improving working conditions."
NZNO chief executive Memo Musa said that strike action was a last resort, but should it go ahead patient safety was paramount.
"We have had several meetings with DHB representatives to begin preparation to ensure patient safety.
"NZNO will work with DHBs to agree provision of life preserving services and we will be absolutely comply with the Code of Good Faith for the public health sector," he said.