Moody's and Fitch Rating agencies affirmed their AAA credit ratings for the U.S. but they warned that downgrades were possible if lawmakers fail to enact debt reduction measures and the economy worsens.

Moody's said in a statement yesterday that the outlook for the U.S. grade is now negative, and this statement came after President Barack Obama signed into law a plan to lift the nation's debt ceiling and cut spending after months of conflicts between Democratic leaders and Republican lawmakers.

According to Moody's Hess, a decision on the rating maybe made within two years, or considerably sooner.

While Standard & Poor had put the U.S. government on notice on April 18 that it risks losing its AAA rating unless lawmakers agree on a plan by 2013 to reduce budget deficits and national debt, the company indicated last week that any cuts of less than $4 trillion would jeopardize the grade.