The U.S. government expects its debt to be downgraded by credit ratings agency Standard & Poor's from its current triple-A rating and is preparing for the event, ABC News said on Friday.

ABC cited an unnamed government official as its source and said it was uncertain whether the rating would drop from triple-A to AA+ or to AA.

The report said the main reasons likely to be cited for a U.S. downgrade by S&P included political confusion surrounding the process of hiking the debt limit and doubt that agreement would be reached on more deficit reductions.

Standard & Poor's warned last month that the United States was at risk of a downgrade if it did not raise the debt ceiling and cut the country's debt by $4 trillion over a decade.