The new strike follows one of 48 hours by that began on October 18. That walkout led to thousands of patients' non-urgent operations or clinic appointments being postponed by the DHBs.
Whanganui board spokeswoman Sue Campion said the DHB had yet to assess the likely impact of the latest planned action. "It's too early to say."
Dr Powell said the decision to strike a second time came after a DHB offer was rejected by the union in mediation. Dr Powell said the offer was not as good as stated by the DHBs.
The dispute involves the union's demands for safer working hours and its assertion that long hours were putting patients and doctors at risk.
On Monday the DHBs said in a press release they had "formally made an offer to the RDA, the union representing registered medical officers (RMOs). The DHBs expected their offer to settle the dispute with the union because it addresses all the health and safety issues raised by the union.
"Surprisingly, in mediation, the offer has been rejected by the union. DHBs believe that in rejecting the offer the union is planning to take further strike action".
Head of the DHBs' Workforce and Employment Relations Programme and chief executive of Whanganui DHB Julie Patterson described the offer as providing "world leading hours, and working conditions for junior doctors".
She said it gave a "contractual guarantee that no RMO would work more than four nights or 10 days in a row".
