Rating agency Moody's expects that the U.S. economic growth in a long-term period will be lower than the average prior to the financial crisis. The slower economic growth can support the US's Aaa rating with stable outlook, Moody's noted. But the rating agency added that the slower growth will make the rating more vulnerable to economic shocks and fiscal policy changes.

Moody's expects the U.S. economy to expand at about 2.8% in 2015 and 2016 due to productivity growth, consumer spending and non-residential fixed investment.