Fed promises to keep rates low at least 2 yrs

I came across this article today, I really wonder if the US Gov't will keep the interest rates "near zero" for the duration of time that they claim to do so, which is 2 years, and, if they go back on their word, what will that do to their rating?

WASHINGTON (Reuters) - The U.S. Federal Reserve, in an unprecedented move, said on Tuesday it will keep interest rates near zero for at least two more years and is considering further action, bolstering battered stock markets.

The Fed's policysetting Federal Open Market Committee, in a 7-3 vote, overcame internal discord in the first triple dissent against a policy decision since 1992.
Investors were still unsure whether the Fed's even stronger promise to maintain rates at rock-bottom lows until mid-2013 would be enough to revive a flagging economic recovery.

But the decision sparked a rally in equities that pushed the Dow Jones industrial average up more than 400 points. Short-term Treasury yields fell to all-time lows. The gains came after a rout that stemmed from Standard & Poor's historic downgrade of U.S. credit quality last Friday.

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