Rio debt rise forces S&P demotion, presses Walsh RAPID expansion in Rio Tinto's debt levels to $US33 billion ($32.1bn) has prompted Standard & Poor's to revise its credit rating outlook to negative from stable, increasing the pressure on Rio's new chief executive Sam Walsh to deliver on his promise of massive operating cost cuts, asset sales and reduced capital expenditure commitments ahead of a possible collapse in iron ore prices. The negative outlook indicates a one-in-three chance of a downgrade on Rio's A-/A-2 long and short-term credit ratings as S&P identifies the current bumper iron ore price of more than $US150 a tonne as being supportive of Rio's position. But the potential for iron ore prices to fall would make Rio's deleveraging plan more of a challenge.