What is Standard and Poor's AAA rating stand for? US president Barack Obama is under growing pressure this weekend after the country's top-notch credit rating was downgraded for the first time ever. Its AAA rating - which it has held since 1917 - now stands one grade lower at AA+.Standard and Poor's (S&P), one of the world's leading credit agencies, said the deficit reduction plan approved by Congress on Tuesday after weeks of wrangling did not go far enough.

To make things worse, S&P has also issued a negative outlook, meaning it could lower the US credit rating again in the next two years.

The downgrade came at the end of a tumultuous week on the world's stock markets sparked by the US debt crisis and renewed fears over the eurozone. John Chambers, chairman of S&P's sovereign ratings committee, said it could have been avoided if the political stalemate over the US debt ceiling had been resolved earlier.

"The first thing it could have done is raise the debt ceiling in a timely matter so the debate would have been avoided to begin with," he said.

The two other main credit agencies, Moody's Investor Service and Fitch, said they had no immediate plans to take the US off their lists of risk-free borrowers.

But both warned that could easily change in the future.

The downgrade is a huge embarrassment for Mr Obama, who has urged US lawmakers to set aside their political differences and work together to help rebuild the economy.

He issued the appeal in his weekly address to the nation recorded just before S&P took away its AAA credit rating.

John Boehner, Republican speaker of the house of representatives, commented: "This is the latest consequence of the out-of-control spending that has taken place in Washington for decades."

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