The U.S., lacking a plan to contain $1 trillion deficits, faces the prospect of another rating cut in six to 24 months depending on the outcome of November elections, according to John Chambers of Standard & Poor’s.

America has had an “AA+” rating with a negative outlook since Aug. 5 when the New York-based unit of McGraw-Hill Cos. stripped the nation of its “AAA” ranking for the first time, citing the government’s failure to agree on a path to reduce deficits. The U.S. has a one-in-three chance of another downgrade, Chamber said Wednesday during an S&P sponsored Webcast.

“What the U.S. needs is not so much a short-term fiscal tightening, but it has to have a credible medium-term fiscal plan,” said Chambers, managing director of sovereign ratings. “That is going to have to say something about entitlements, and that is probably going to have to say something about revenues.”

Bond investors ignored the downgrade, driving Treasury yields to the lowest levels in history, amid concern the U.S. economy was stalling and as Europe’s debt crisis intensified.

Treasuries have returned 3.9 percent since the rating cut and gained 9.8 percent last year, the debt’s best performance since 2008, according to Bank of America Merrill Lynch index data.

“I don’t think anything is going to happen between now and the election in November,” Chambers said.

S&P said in August that political brinkmanship over increasing the government’s debt ceiling year showed the U.S. is becoming “less stable, less effective and less predictable” as the Treasury almost reached its borrowing limit before the government reached a compromise.

The “political brinkmanship hasn’t gone away,” Chambers said today. “That simply doesn’t happen in other ‘AAA’ economies.” 

(Bloomberg)