The Defence Force says the operation to remove fuel from the sunken survey ship off Samoa should begin on 16 December.
The Manawanui sank in October when the crew did not take it off autopilot in time and it hit a reef.
Defence leaders told a scrutiny session by a select committee at Parliament on Tuesday afternoon that the fuel salvage was getting into place.
"We're advised by the salvage company that the process to extract the oil ... will take around 20 days," chief of the Defence Force, Tony Davies, told MPs.
Bad weather or other complicating factors could push that out, he said.
Earlier in the session, Defence Minister Judith Collins rejected a suggestion by Labour's Peeni Henare that villagers near the site were unhappy at lack of support from the Navy and lack of action on the salvage.
Henare said he heard from sources on the ground, at the site on the south coast of Upulo.
Collins said the navy had been "scrupulous" and "exemplary" in their behaviour.
The navy did not ask for this, and no one set out to sink it, but "clearly a few people have had a terrible day's" work, Collins said.
However, it was not a tragedy, because 75 body bags did not come home, she added.
The offshore patrol vessel Otago is now getting ready to head out to pick up on Manawanui's job.
The navy would go back out "with our tails up, not down", the minister said.