Standard & Poor's revised on Wednesday its rating outlook on the country's largest private sector firm Reliance Industries [Get Quote] to negative from stable on the back of the company's increased debt and pressure on profitability.

The downturn in commodities and oil refining, stemming from global economic slowdown, has affected profitability. This is expected to weaken the company's cash flow measures, S&P said.

"Profitability, however, is expected to be adversely affected by lower fuel demand, especially in developed markets," S&P's credit analyst Mehul Sukkawala said.

Meanwhile, S&P has affirmed its BBB long-term corporate credit rating on Reliance Industries.

This rating suggests the bonds are of medium grade quality.

Security currently appears sufficient but may be unreliable over the long-term.

The company's gross refining margins have softened to $13 per barrel in the September quarter, from $15 per barrel in the fiscal year ended March 2008.

S&P projects refining margins to dip further to $9-10 per barrel in near term.

The global credit rating agency further said the outlook could be revised back to stable on evidence of improved leverage and resilience in the face of the current commodity and refining cycle downturn.

The cash flow measures of Reliance Industries are expected to improve after its Jamnagar refinery becomes fully operational and we expect its production to be ramped up to almost full capacity in fiscal 2010.

The refinery came on-stream in December this year.

RIL has a liquidity position of about $5.3 billion as on November 30 this year, enough to cover about $3billion debt due in one year, S&P added.