She said it was "extremely disappointing" that the resident doctors had seen no other way to resolve the dispute.
"The DHB's resistance to meaningfully improve current unsafe rostering practices has left us no choice," Dr Powell said.
"We have yet to see sufficient real change in the system after four years of engagement and 10 months of bargaining."
"We see no other way to secure safer rosters for doctors and the patients we care for."
Last week, Dr Powell told the Chronicle that while health boards had made offers such as reducing night shifts from seven in a row to four in a row, and making a commitment to address doctors working 12 days in a row, the changes wouldn't happen for another two years.
There has been no indication so far as to how Whanganui District Health Board will handle medical cover during the strike.