Moody's: Why we're not downgrading U.S. yet

NEW YORK (CNNMoney) -- Moody's Investors Service explained Monday why it was sticking with its triple-A bond rating and negative outlook for the United States, setting itself apart from Standard & Poor's, which downgraded the U.S. last week.

Moody's said it expects the economy will improve and additional measures to reduce the budget deficit will be in place by 2013. The rating agency said this is why it reiterated its AAA rating for U.S. debt on Aug. 2, when the Senate agreed on a 10-year plan to reduce the deficit by more than $2 trillion.

But Moody's said that its negative outlook, which it also assigned on Aug. 2, was due to political squabbling in Washington -- the biggest potential threat to the bond rating.

"We expect the economic recovery will continue and additional budget deficit reduction initiatives will be put in place by 2013," said Moody's, in its report on Monday. "The political parties now appear to share similar deficit reduction objectives."

But Moody's also said, "However, the disagreement between the two parties over the means by which to achieve deficit reduction and the difficulties experienced in reaching a compromise on raising the debt ceiling highlight the risks of political polarization. This uncertainty is among the drivers of our negative outlook."