Ms Ardern is to make an announcement tomorrow about health during her first visit to Dunedin as leader.
It comes days after Prime Minister Bill English's controversial rebuild announcement.
When asked, the party's Dunedin Labour MPs would not confirm details.
It is likely to be Labour's hospital rebuild plan.
The possibility of a privatised rebuild draws a clear dividing line between the parties ahead of the election. Labour is opposed to a public-private partnership.
Ms Ardern is likely to promise a central-city rebuild.
Last Saturday Mr English said the Government was keen to pursue the possibility of a privately funded hospital.
Mr English said he had a strong preference for a central-city site, but if that was not possible, it would be rebuilt at the Wakari Hospital site.
After years of delay and publicity about the leaking clinical services building, the promise of a new hospital was met with relief, but also scepticism.
