Meridian Energy expects to have further discussions with Rio Tinto before Christmas about its contract to supply electricity to the Bluff aluminium smelter.
Rio Tinto wants a lower price for electricity to the smelter, which has cut jobs and is facing further cuts due to the global economic downturn and a drop in the price of aluminium.
Meridian, a State energy company, has an 18 year contract with New Zealand Aluminium Smelters, which was agreed in 2007 and commences at the beginning of 2013.
Rio Tinto owns Pacific Aluminium, which is a major shareholder in the smelter company.
About 15% of Meridian's output goes to the smelter.
Meridian chief executive Mark Binns said Rio Tinto has requested that it look at the contract and make a decision as to whether the company is prepared to alter it in a number of ways.
Mr Binns said he could not comment on where the company has drawn the line in the negotiations.