About 2500 ambulance officers who work for Hato Hone St John took strike action for the first time ever on Tuesday.
Members of the New Zealand Ambulance Association and First Union did not work the first four hours of their shifts.
Rallies were held in Auckland, Palmerston North, Christchurch and Invercargill.
Ambulance officers have been negotiating over pay and conditions with the employer, St John, since their Ambulance Operations Multi-Union Collective Agreement expired in December 2023.
The unions - New Zealand Ambulance Association and First Union - had rejected a settlement proposal by St John last week.
St John deputy chief executive of ambulance operations Dan Ohs said it had made two separate offers that attempted to pass on available funding from Health New Zealand and ACC, which had fallen short of union expectations.
Union representatives said the proposed settlement dealt with none of the unions' combined claims beyond pay increases and still represented a real-terms pay cut for ambulance officers.
On Tuesday, New Zealand Ambulance Association division chairman Mark Quin said he had heard nothing from St John since strike action began at 4am.
"We're always happy to talk and discuss and meet, and we've been prepared to do that all the way along at any time with no barriers," he said.
"We're hoping that this highlights to the public, the politicians and to the funding agencies, the dilemma that we are in, and the issues that are current around settling a pay dispute and the wider funding issue for St John and providing ambulance services across New Zealand."
Ohs said, instead, the collective focus of St John was making sure that the community was safe.
"Of course, we will pick up the phone and have some direct conversations in the morning. But for today, our focus is on making sure that patients get a safe response from our service.
"There's been no further discussion with us around funding yet. And again, that's a conversation I would be looking to pick up with them in the morning."
Quin said St John needed to be 100 percent funded by the government. The ambulance service was currently 82 percent funded.
First Union national ambulance coordinator Faye McCann added the New Zealand Ambulance Association and First Union had been told that no funds are available for pay negotiations, despite the government's commitment to increase funding to the partially charity-funded service.
"We're calling for the government to live up to their promises and fully fund the ambulance service not just to end these drawn-out pay talks, but for the future of our emergency services in New Zealand," she said.
"Without solving the issue of funding now, we will be back in the same position next year and the year after that before the government finally acknowledges that we can't run an effective ambulance service when we're relying on charity donations and austerity."
Ohs said St John has made it clear in discussions with Te Whatu Ora/Health New Zealand and ACC that it would like to move to a position where 100 percent of its operating costs - the day-to-day cost to run the service, such as paying staff - were funded.
He said St John could not afford to improve on its current pay offer without more government funding.
Health New Zealand and ACC currently provide around $380 million a year in total to St John and Wellington Free Ambulance for emergency road ambulance services, an 32 percent increase over the past two years.
Strike action on Tuesday will conclude at 4am on Wednesday, but is set to continue on Saturday 24 August, with a 'Life Preserving Service Agreement' negotiated and in place with St John to ensure minimum ambulance coverage for serious medical issues during strike actions.