New Zealand authorities are trying to board a vessel caught illegally fishing in the Southern Ocean.
Foreign Affairs Minister Murray McCully said approval to board was granted to the Navy's offshore patrol ship the HMNZS Wellington in the last two to three hours.
But he told Newstalk ZB that was only the first step.
He says the fact authorities have got approval does not mean they will get onboard.
Mr McCully said the safety of the New Zealand crew must be put first in what could be a dangerous situation.
Earlier Mr McCully had said he wanted to "throw the book at" three fishing vessels caught by New Zealand navy patrols illegally taking lucrative toothfish from the Southern Ocean fishery.
Mr McCully said the ships, believed to be working as a syndicate, were "making a mockery" of the tightly regulated and quota-managed fishery in the icy waters around Antarctica.
"I've told the ministry I want to throw the book at them," he said. "I've signalled to the New Zealand agencies involved that ... we want to put these guys completely out of business and take whatever steps we have to achieve that."
The Songhua, the Kunlun and the Yongding were not licensed to fish in the region and navy officials had observed them over the past week using banned fishing methods such as gillnets.
The minister said there had been "too many slaps across the wrist with a wet bus ticket" in previous illegal fishing cases, and he would pursue diplomatic and legal avenues to punish the countries the ships were linked to.
Two of the ships were on an illegal fishing blacklist.
All three were flagged to Equatorial Guinea but at least two had been linked to a Spanish syndicate called Vidal Armadores SA.
A New Zealand Defence Force spokeswoman said the Ministry of Foreign Affairs and Trade (Mfat) was the lead agency involved in the operation.
Comment was being sought from Mfat.
- additional reporting Isaac Davison