Planned industrial action affecting more than 1000 ambulance officers throughout the country is linked to similar issues involved in the junior doctors' national 48-hour strike, which starts today.
First Union ambulance professionals co-ordinator Lynette Blacklaws said ambulance officers had issued a 14-day notice of industrial action.
The strike came after an attempt by St John to squeeze more out of already stretched frontline staff.
"We are seeking solutions to issues that cause dangerous fatigue, such as not receiving rest and meal breaks coupled with an increased workload,'' she said.
The notice comes on the eve of the junior doctors' strike. St John staff have expressed similar concerns about fatigue and understaffing.
Details of how Dunedin and Otago would be affected by the planned strike were not immediately available yesterday, but ambulance officers throughout the country will continue to respond to callouts.
Ms Blacklaws said the planned overall action included a ban on paperwork, and would disrupt St John's ability to invoice patients, but officers wanted to protect patient safety.
St John human resources management officials said the organisation had just received notification from the five unions representing staff and was considering
it.
St John was in the middle of collective bargaining with the unions and had agreed to mediation before the notification was issued.
St John would continue to work in good faith and to discuss relevant issues "directly with unions and our staff'', management officials said.
St John posted a $7.5 million deficit for the 2015-16 year, media reports say.
Government funding covers 70% of the running costs of the service. The rest comes from public donations.
