The 24-hour strike is set to begin on July 30. Photo: RNZ

More than 36,000 Te Whatu Ora nurses, midwives, health care assistants and kaimahi hauora have voted to strike for 24 hours over what they say is a failure by Health New Zealand to address safe staffing concerns.

The Nurses Organisation took a ballot of its members on possible industrial action that would begin with a 24-hour strike on July 30.

Other actions would follow.

Health NZ is offering a 3% pay rise over two years, plus two payments of $325.

The union said the agency was refusing to provide safe staffing levels in its latest contract offer.

Health NZ's latest pay offer was a "massive backward step" for the health system and patients and there were "very strong indications" members will want to strike, the union said.

Health NZ told RNZ it was committed to reaching an agreement, but it was also "operating within tight financial constraints".