An open ocean tugboat is on its way to rescue an oil and chemical tanker stuck off the coast of Stewart Island.

Maritime NZ said the Golden Mind tanker got into steering difficulties west of the island on Wednesday, and the ship and crew had remained there since then.

"We have been informed that the owners of Golden Mind has contracted the ocean-going tug MMA Vision to provide towage assistance," Maritime NZ said.

"Towage arrangements are made between the commercial parties involved - in this case, Golden Mind's owners and MMA Vision."

MMA Vision set off from Wellington on Thursday and was expected to reach the stuck tanker Sunday afternoon.

MMA Vision (marked in blue) set off from Wellington on Thursday and was expected to reach the stuck tanker (marked in red) Sunday afternoon. Photo: Marine Traffic

The plan was to tow the vessel to Timaru.

No distress calls had been issued and its Rescue Coordination Centre continued to monitor the situation, Maritime NZ said.

The MMA Vision tugboat had been contracted by the government as a standby tug for the Cook Strait ferries.