S&P said Thursday afternoon that it was putting GM on its "creditwatch," with negative implications. The ratings agency said the move reflected the rapid weakening of most of the world's auto markets. It added that capital conditions in the sector would remain challenging for the "foreseeable future."
The agency also put the 49 percent GM-owned finance affiliate, GMAC, on creditwatch as well.
GM said earlier Thursday that car sales in Europe fell 1.9 percent to 1.6 million vehicles in the first nine months of the year, dropping its market share by 0.2 percentage point to 9.3 percent in that market.
It blamed the credit crisis and inflation for seriously hurting consumer confidence.
"We are facing an unprecedented set of economic challenges due to the global economic crisis," GM Europe President Carl-Peter Forster said in a statement.
GM, a component of the Dow Jones Industrial Average, said Tuesday it was cutting production in Europe, as fears of an economic downturn hurt sales on the Continent as a whole, despite ongoing gains by the company in Eastern Europe.
GM, the largest U.S.-based automaker, posted a $15.5 billion net loss in the second quarter and announced plans in July to cut costs by about $10 billion.