(Bloomberg News) Standard & Poor's said it was an "oversimplification" to blame its stripping the U.S. of the top AAA sovereign rating for recent market volatility, adding that many investors agreed with its action.

Markets were also responding to a weaker global growth outlook, David Beers, global head of sovereign and international public finance ratings at S&P, told reporters in Singapore today. The company is untroubled by dissenting views on its decision, he said in response to questions.

His comments follow criticisms by investors including Warren Buffett, the world's most successful investor, who said that the U.S. should be "quadruple-A" and the decision doesn't reflect any inability of the U.S. to pay its debts. The market value of global stocks plunged by $7.6 trillion between Aug. 5 and Aug. 12, according to data compiled by Bloomberg, after S&P cut the U.S. by one level to AA+ on Aug. 5, citing the political failure to reduce record deficits.

The Obama administration criticized the S&P move, with the Treasury Department telling the company it had overestimated future national debt by $2 trillion. S&P said the discrepancy didn't affect its decision, and based its conclusion on the U.S. government becoming "less stable, less effective and less predictable."

The U.S. growth trajectory faces downside risks, and the medium-term fiscal adjustment in the world's biggest economy may be impacted by a slowdown, Beers said today. An AAA rating for the U.S. isn't likely in the near term, he said.

The underlying trend of demand in Japan remains quite weak, and S&P is still waiting for the country's fiscal consolidation plan, he said. Asian economies are still fighting inflationary pressures and the region's ratings face downside risks from the U.S. and Europe, S&P said.