By Stephen Wright

WELLINGTON, New Zealand--Rio Tinto Ltd. said it isn't planning to restart a fourth production line at the Tiwai Point aluminum smelter in New Zealand.

Reports in New Zealand media citing smelter staff have said Rio Tinto will restart the line in September, raising hopes the mining giant could delay plans to permanently shut the smelter by the second half of next year.

"We have no current plans to restart Line 4," a Rio Tinto spokesperson told The Wall Street Journal on Friday.

The smelter consumes about 13% of New Zealand's electricity and its closure is expected to affect earnings of power-generating companies such as Meridian Energy Ltd., Contact Energy Ltd. and Genesis Energy Ltd.

Write to Stephen Wright at stephen.wright@wsj.com