Standard & Poor's (S&P), the ratings agency, has placed 13 US companies on credit watch because of their pension fund deficits, after taking similar action in Europe earlier this year.

Alcoa, Allegheny Technologies, Caterpillar, Caterpillar Financial Services, Consol Energy, Cummins, Delphi, Eaton, Kimberly-Clark, Pittston, PPG Industries, SBC Communications and Visteon are all in danger of having their corporate credit ratings downgraded.