Standard & Poor's Ratings Services kept on going Monday, downgrading the credit ratings of Fannie Mae and Freddie Mac and other agencies linked to long-term U.S. debt. On Friday, the S&P stunned the financial world by downgrading the United States one notch from AAA.

Besides downgrading Fannie Mae and Freddie Mac Monday, S&P also lowered its ratings for farm lenders, long-term U.S. government-backed debt issued by 32 banks and credit unions and three major clearinghouses used to execute trades of stocks, bonds and options.

All downgrades were from AAA to AA+.

S&P said the agencies and banks downgraded all have debt exposed to economic volatility and a further downgrade of long-term U.S. debt. S&P noted that the creditworthiness of the downgraded entities relies upon the government's ability to pay its own creditors.

The downgrades pushed struggling U.S. markets lower Monday. After the announcement, the Dow was down nearly 300 points, or 3.2 percent, while the S&P stock index dropped almost 5 percent.

S&P said Fannie and Freddie, which own or guarantee roughly half of all U.S. mortgages, were downgraded for "direct reliance" on the U.S. government.

In downgrading the U.S. debt rating Friday, setting off spiraling drops in financial markets around the world, S&P declared it lacks confidence in America's political leaders' ability to avoid a long-term debt crisis.