Junior doctors will walk off the job next month for 48 hours over concerns about the pay deal being offered to them by the country's district health boards.
The strike would include up to 3300 resident doctors and run for two days, beginning at 7am on January 15, the New Zealand Resident Doctors Association said.
The union and its doctors last went on strike in 2016 in the lead-up to successfully securing better working conditions as part of a "safer hours" campaign, RDA national president Dr Courtney Brown said.
However, in the current round of negotiations, the DHBs had been trying to "claw back" some of the improved conditions the doctors won in 2016, she said.
"Whilst in 2018 most health workers gained improvements to terms and conditions
of employment without facing claw backs, the DHBs have taken a distinctly different approach to resident doctors," Brown said.
"It feels like they are punishing us for our successful safer hours campaign."
DHB spokesman Peter Bramley said the strike action was regrettable because the DHBs had made a good offer that built on past negotiations to deal with stress and fatigue.
"We're not interested in clawing back conditions as suggested but rather are looking for options that allow greater local flexibility in work patterns that support better training and improved clinical care," he said.
He said the DHBs had also already made a new deal with the Specialty Trainees of NZ - a separate union representing a smaller number of resident doctors.
A spokeswoman for Duty Minister Stuart Nash said the Government was not a direct party to the pay negotiations but was disappointed they had broken down.
She urged both the DHBs and the Resident Doctors Association "to keep talking to find a solution".
The planned strike would hit hospitals across the country, but would not put patients' lives at risk, RDA national secretary Dr Deborah Powell said.
"The resident doctors are the main labour force for doctors in the hospitals," she said.
"But there will be other doctors on duty - mostly senior doctors - who will be looking after patients instead of us."
She said the union was still open to negotiations and hopeful a resolution could be reached before the strike was needed.
DHB spokesman Bramley said hospitals had made contingency plans to ensure emergency and essential services would be available.
"The union's timing is cynical and DHBs will do what they can to try and avoid the strike, but will be ready if a negotiated solution can't be found," he said.
During the 2016 industrial action, resident doctors complained they worked up to 12 consecutive days with some of the shifts being 16 hours' long, which was unsafe for patients and too tiring for them.
After "quite a bitter" dispute with DHBs, the doctors managed to win improved conditions, Powell said.
However, during the latest negotiations that have been going on since February, the DHBs were now trying to "claw back" some of the pay, training and reduced working hours concessions granted to doctors, she said.
Powell said the DHBs' actions were disappointing because it had become widely recognised across the globe that doctors "need to look after themselves to be capable of looking after their patients".
"If we're not well trained, if we're not well rested, if we don't have a good work-life balance, if we don't have a good family life - we're not the doctors we need to be to care for our patients," she said.
Powell said that even after the last successful round of negotiations doctors still worked long hours of about 55-60 hours a week.
"We don't mind working hard but there has got to be some fairness in this," she said.
There are more than 4000 resident doctors in New Zealand, ranging from first year medical graduates to doctors with 8-10 years' experience who are about to qualify as specialists.
While the RDA represents the bulk of all resident doctors, the DHBs recently concluded a pay deal with the Specialty Trainees of NZ union representing a smaller number of resident doctors.
This deal included pay rises of 2.5 per cent and 3.0 per cent before December 2020 and a new roster system.