Standard & Poor’s announced Friday night that it has downgraded the United States credit rating for the first time, dealing a huge symbolic blow to the world’s economic superpower in what was a sharply worded critique of the American political system.

Lowering the nation’s rating one-notch below AAA, the credit rating company said “political brinkmanship” in the debate over the debt had made the U.S. government’s ability to manage its finances “less stable, less effective and less predictable.” It said the bi-partisan agreement reached this week to find $2.1 trillion in budget savings “fell short” of what was necessary to tame the nation’s debt over time and predicted that leaders would have no luck achieving more savings later on.

The decision came after a day of furious back-and-forth between the Obama administration and S&P. Government officials fought back hard, arguing that S&P made a flawed analysis of the potential for political agreement and had mathematical errors in its initial analysis, which was submitted to the Treasury earlier in the day. The analysis overstated the U.S. deficit over 10 years by $2 trillion.