Salvors on the grounded container ship Rena say they are very hopeful they will be able to finally pump oil from the submerged starboard fuel tank on Wednesday morning.
750 tonnes of seawater has had to be pumped into the tank so the 360 tonnes of heavy fuel oil inside will rise to the top.
The fuel is the last remaining oil on the vessel which ran aground on Astrolabe Reef off the coast of Tauranga on 5 October.
Svitzer salvage master Drew Shannon says pumping started on Monday night but an air pocket developed, stalling work.
An observation flight took place over the ship on Wednesday morning and no change in Rena's condition was detected.
A skeleton crew of three remained on the ship overnight.