The Wall Street Journal reports S&P, issuing its most explicit warning yet that General Motors (GM) is at risk of filing for bankruptcy protection, slashed GM's credit rating deeper into "junk" territory and warned that Chief Executive Rick Wagoner's restructuring plan may not be enough to turn the co around. "We're saying bankruptcy is more of a possibility than had seemed to be the case previously given the deterioration in their business prospects and their financial condition," S&P credit analyst Scott Sprinzen said in an interview. S&P downgraded GM's corporate credit rating two notches to a B, with a negative outlook, from a previous rating of double-B-minus. With its move, S&P put the co in a category of firms more likely to default -- the share of single-B rated companies that default within one year is about 5.7%, while the comparable default rate for double-B rated companies is 1.2%