TVNZ had said that Petrie would continue to present across its news and current affairs shows in a support presenter role.
The broadcaster said there would be no crossover between the red and the blue teams "ensuring 1 News can continue even if one group is impacted by Covid-19."
Hayley Holt, who had her last day on Breakfast this morning, will move forward her first presenting day with 1 News Sport to Monday.
In order to achieve this, Tonight would come off air temporarily and staff redeployed to support the split news team.
Weekday news programmes, Breakfast and Seven Sharp would retain their regular presenting line-up.
"Presenters in these teams will sit separately from the wider newsroom. Melissa Stokes and Anna Burns-Francis will appear in the Breakfast newsreader role while a permanent replacement is found to cover Jenny-May Clarkson's move into the show's presenting chair. "
There would be no impact to weekly shows Fair Go and Sunday.
TVNZ confirmed it was moving to a solo anchor format in July with Dallow remaining at the helm. Petrie had presented alongside Dallow for 14 years. (edited)
Earleir today, Petrie talked to Coast Breakfast hosts Jason Reeves, Toni Street and Sam Wallace about the pressure of her job and what she would miss most about presenting the news alongside Dallow.
"I really enjoy getting out there and pushing myself. I mean it's a funny thing, I actually really love that adrenaline buzz, I like the nerves and the tension.
"When you're on edge, when you're on TV and you're live and it's just you and the pressure's on."
Petrie said she had been "blown away" by the positive messages from viewers since TVNZ confirmed she was leaving her role.
"I've just been blown away... it's quite an insular world 'tele', you go in, you do your job you read the news you come home you put the kids to bed.
"I always assume that [they] hate what [I'm] wearing, they don't like my lipstick, or that you've stuffed something up last night, but it's so nice to have had so many nice messages and I'm just so blown away."