The U.S. Senate Banking Committee is looking into the decision by Standard & Poor's to downgrade the nation's credit rating for the first time in history, according a committee aide briefed on the matter.

Senate Banking Committee Chairman Tim Johnson, a South Dakota Democrat, is gathering more information on the Aug. 5 decision, which has been criticized by Treasury Secretary Timothy F. Geithner and other officials in President Barack Obama's administration, according to the aide, who declined to be identified because he wasn't authorized to discuss the matter publicly.

"This irresponsible move by S&P may, however, have spillover effects that tax the American people by increasing interest rates on home loans, credit cards, and car loans, and by increasing the cost of finance for some state and local governments," Johnson said in a statement today. "I am deeply disappointed in S&P's decision to enter into the game of political punditry."