Outside the New York Stock Exchange on Wall Street. 

Moody's has warned that it could cut the credit ratings of the six biggest US banks, saying the federal government may be less likely to bail them out if they got into trouble in the future.

Goldman Sachs, JPMorgan Chase, Morgan Stanley and Wells Fargo could be downgraded, the rating agency said on Thursday. The ratings of Bank of America and Citigroup are also under review, but with "direction uncertain", Moody's said.