Standard & Poor's focused too much on the messy political process leading to a debt-limit hike and made a $2-trillion error in its calculations about U.S. finances, sources familiar with the discussions claimed on Friday night.

The error was centered in the ratings agency's estimates of discretionary spending and was pointed out by Treasury and it raised questions about S&P's credibility, the sources said.

A Treasury spokesman also raised the issue of the huge error, reflecting administration concern at S&P's decision to downgrade U.S. debt.

"A judgment flawed by a $2 trillion error speaks for itself," the Treasury spokesman said.

S&P S&P