Benchmark crude fell by 40 cents to end at $98.70 per barrel in New York. Brent crude, which is used to price foreign oil that's imported by U.S. refineries, fell by 70 cents to end at $110.35 per barrel in London.
The downgrades could make it harder for the European Union to raise money and overcome massive government debts. A recession appears likely in Europe, and huge spending cuts will likely reduce European energy demand this year.
In the U.S., gasoline pump prices rose 1 cent to a national average of $3.39 per gallon, according to AAA, Wright Express and Oil Price Information Service.
In other energy trading, heating oil fell 3 cents to finish at $3.03 per gallon, while gasoline futures were virtually unchanged at $2.73 per gallon. Natural gas fell 3 cents to $2.67 per 1,000 cubic feet.