MELBOURNE, Aug 31 (Reuters) - Standard & Poor's warned on Monday it was likely to revise the credit ratings for some miners over the next week after cutting its price forecasts for aluminium, copper, zinc, nickel and gold and said it expected prices to remain volatile.
The rating agency slashed its nickel forecasts the most, by nearly 25 percent to $5 a pound for the rest of 2015 and $5.50 a pound in 2016, which could affect ratings for Brazil's Vale and Russia's Norilsk Nickel's.
S&P cut its aluminium price forecasts by 18 percent to $0.70 a pound for the rest of 2015, and by 12 percent to $0.75 for 2016. It cut its outlook for copper prices by 11 percent to $2.40 a pound for the rest of this year, 2016 and 2017.
However it raised its iron ore forecast for the rest of this year by $5 to $50 a tonne and sees the price holding there in 2016.
"At this stage, we expect to take only selective rating actions," S&P said. These would be based on a company's flexibility to adapt to weaker prices by cutting spending and shareholder payouts.
"We anticipate, however, that commodity prices will remain very volatile while the slowdown in China has increased uncertainty; we will continue to closely monitor companies' ability to absorb shocks over the coming months."
S&P and Moody's warned last week that top global miner BHP Billiton's credit ratings might come under pressure in the 2016 financial year if commodity prices remained weak and the company continued to raise its dividend.
S&P now sees gold prices averaging $1,150 an ounce over the next two years, down from a forecast of $1,200.
Reporting by Sonali Paul; Editing by Richard Pullin