WASHINGTON - US Treasury Secretary Timothy Geithner late Sunday criticized Standard & Poor's downgrade of the country's credit rating from AAA to AA+ as a "terribly poor judgement".

S&P Friday removed for the first time the AAA long-term sovereign credit rating for the United States and lowered it by one notch to AA-plus.

Geithner said the agency's decision showed a "stunning lack of knowledge" about the basic math used to develop the federal budget.

In recent days, several senior US officials have complained S&P's analysis is poorly and hastily done.

"We have a very resilient economy. We're a very strong country and I have enormous confidence in the basic regenerative capacity of the American economy and the American people," he said in an interview with NBC News.

"By moving so quickly, they made the wrong decision without the right information," a senior Treasury official told Xinhua Saturday on condition of anonymity.

Geithner Sunday announced in a statement he has informed President Barack Obama that he will remain on his job, amid rumors that he was considering resignation once a deal on raising the US debt ceiling was inked.

Obama Tuesday signed a bill lifting the nation's debt limit through 2013 and cutting the deficit by more than $2 trillion, but the deficit reduction package fell far short of a threshold of $4 trillion cited by S&P to avoid a downgrade.