Newmont Mining Corp, one of the world's largest gold producers, said Friday that power outages have affected operations at its Ahafo mine in Ghana, prompting it to cut a monthly production forecast by at least 35 per cent.

The Denver-based mining giant said it is looking at alternatives, including diesel generators that could provide electricity but could take up to 60 days to install.

The Volta River Authority, the wholesale power utility in Ghana, asked Newmont and other companies that use large amounts of electricity to cut consumption as much as 50 per cent at the Volta Reservoir, which serves a hydroelectric plant but has low levels of water.

Newmont's subsidiary, Newmont Ghana Gold Ltd, agreed to intermittent shutdowns and to stockpile ore while alternatives are sought, the company said in a Securities and Exchange Commission filing.

Monthly production will be cut between 35 per cent and 60 per cent, Newmont said. Costs related to those gold sales were expected to increase as much as 20 per cent.

The filing came amid a spate of issues that Newmont has faced at its overseas operations.

In Manado, Indonesia, Newmont executive Richard Ness took the stand Friday in a criminal trial and denied that his company dumped dangerous levels of mercury and arsenic-laced waste into an Indonesian bay, sickening villagers. A verdict is not expected for several months.

Newmont earlier this week reached a deal with protesting farmers who caused a temporary closure of a mine in Peru.