Brutal selling sent the major markets down between 5% and 7% today in the wake of Standard & Poor's downgrades and fears about the economy. In a bid to reassure investors earlier, President Obama said that the nation's problems are "eminently solvable" and that he hopes for a "renewed sense of urgency" to tackle the debt.

Update at 5:05 p.m. ET: Final numbers: Dow closed at 10,809.85, a loss of 634.76 points, or 5.55%.

The S$P 500 ended at 1,119.46, a drop of 79.92 points, or 6.66%. (Uh-oh, the "devil's number" ...)

The Nasdaq finished at 2,357.89, a daily loss of 174.72 points, or 6.9%.

Update at 4:12 p.m. ET: Keep in mind that hedge funds and other investors that had bet against the markets and were "short" made big money today. And remember that for every seller there was a buyer.

Update at 4 p.m. ET: At the close, the Dow was down 633 points, 5.5%; the Nasdaq lost 6.9% (175 points) and the S&P was 6.6% in the red (80 points). Look for slight revisions in those totals as the final tallies are calculated.

Update at 3:58 p.m. ET: Two-minute warning: Dow down almost 600 points, 5.2%. The Nasdaq and S&P continue to trade at losses of more than 6%.

Update at 3:54 p.m. ET: Gold futures closed the day at $1,713 an ounce, but in after-hours trading, December gold has hit a historic high of $1,723.40.

Update at 3:50 p.m. ET: With just 10 minutes to go, selling has driven the Dow down more than 600 points again, or 5%. The Nasdaq and S&P are both off more than 6%.

Update at 3:46 p.m. ET: Crude oil closed at $81.31 a barrel, a drop of $5.57.

Update at 3:32 p.m. ET: With less than 30 left in the normal trading day, the Dow is down more than 500 points, 4.5%, while the Nasdaq is off more than 130 points and the S&P is 65 points in the red, both nearly 5.5%.

Update at 3:23 p.m. ET: Prices for U.S. Treasuries are soaring as investors flee stocks for government bonds, despite the S&P downgrade. The so-called flight to safety is a sign that investors are acknowledging the risks of a deteriorating economy and that the United States remains one of the world's safest havens, Reuters points out.

Update at 3:10 p.m. ET: The Dow has clawed back somewhat, down now around 430 points, almost 4%. The Nasdaq and S&P are deeper in the red, about 5%.

The tech-heavy Nasdaq is off more than 120 points, the S&P 55.

By Douglas Stanglin

USA TODAY

As U.S. stock markets sink, President Obama says he hopes for a "renewed sense of urgency" to tackle debt problem.

Update at 2:30 p.m. ET: The Dow plunges 600 points, sinking below 11,000.

Update at 2:07 p.m. ET: Obama: "We've always been and always will be a triple-A country."

Update at 2:06 p.m. ET: Obama: "The fact is we didn't need a rating agency to tell us we need a balanced, long-term approach to deficit reduction..."

Update at 2:04 p.m. ET: The president calls for tax reform and a "modest adjustments" to Medicare.

Update at 1:59 p.m. ET: Obama says the problems are "eminently solvable," adding that "we know what we have to do."

Update at 1:57 p.m. ET: President Obama says he hopes the debt downgrade will "give us a renewed sense of urgency" to address long-term deficit problems.

Update at 1:45 p.m. ET: The Dow Jones Industrial dropped steeply this afternoon, falling below 425 points for a loss of 3.73%. Nasdaq fell 118 points, for a loss if 4,7% and the S%P down 55 points for a 4.6% drop.

Update at 1:27 p.m. ET: The market drop is holding steady, with the Dow off 325, for a loss of almost 3%, the S&P down 44 points for a 3.75% loss and the Nasdaq down 98 for a loss of just under 3.9%.

Update at 12:56 p.m. ET: Gold rockets to $1718.

Update at 11:49 a.m. ET: The FTSE 100 closes down 178 points at 5069, a drop of of 3.39%.

STREET TALK: Analysts react to market woes

Update at 11:48 a.m. ET: President Obama is expected to issue a statement on the economy at 1 p.m. ET.

WATCH: 1 p.m. ET statement by Obama.

Update at 11:28 a.m. ET:Sharp plummet eases slightly, as DJIA crawls back from 360-point drop.

Update at 10:44 a.m. ET: The U.S. markets reflect sagging performance in Europe, where the FTSE 100 is down almost 3% and the DAX is down over 4%.

Update at 10:39 a.m. ET: DJIA falls more than 360 points, or more than 3%. NASDAQ is off almost 100 points, for just under 4%, while S&P is off 42 points, or 3.5%.

Update at 10:27 a.m.ET: Dow sinks more than 350 points, S&P 500 down over 40 and Nasdaq falls over 100 points.

Update at 10:20 a.m. ET: Stocks continue to stumble as Fannie Mae, Freddie Mac debt downgrades follows downgrade of U.S. government debt.

Update at 10:18 a.m. ET: The Dow plummets 290, as stock markets drop more than 2%.

Update at 9:53 a.m. ET: The U.S. stock markets dropped sharply at the opening, then edged up slightly, with the Dow settling in at around a 2% loss.

Update at 9:36 a.m. ET: DJIA drops sharply at the opening, but begins slow crawl up.

Update at 9:33 a.m. ET: The Dow tumbles over 220 points at the opening, S&P down 26 and NASDAQ off 77.

Update at 9:32 a.m. ET: U.S. stocks tumble at the opening. That follows a drop in markets in Asia by more than 2%. Taiwan took a beating, falling more than 5%.

Update at 9:30 a.m. ET: Stock market opens.

Update at 9:05 a.m. ET: With stock futures pointing to a sharp drop on Wall Street at the opening, the AP acknowledges the impact of the S&P downgrade of U.S. government debt, but adds that the bigger issues for Wall Street and global markets remain debt-ridden countries in Europe and concerns that the global economy is weakening.

Update at 8:57 a.m. ET: Moody's reiterates today that its continued support for AAA rating for U.S. debt is contingent on progress in further deficit reduction. The rating agency says the budget deal last week opens the possibility for additional cuts, but warns that it might reconsider its position if the fiscal or economic outlook weakens significantly, Reuters reports.

Update at 8:51 a.m. ET: Gold price tops $1,700 for first time as investors seek safety after the downgrade of U.S debt.

Stock futures are down 2%. That follows a tough day on Asian and European markets.

"(I)investors with a shorter time horizon may need to brace for some pain and even cut losses following the Standard & Poor's downgrade of U.S. debt," writes CNBC's Jeff Cox. "But those with a longer time horizon can likely stand pat."

The stage was set by S&P's decision on Friday to downgrade the U.S. credit rating from AAA to AA+.

Treasury Secretary Timothy Geithner went on damage-control duty over the weekend, saying S&P has shown "really terrible judgment and they've handled themselves very poorly."

In an interview with CNBC, the secretary said the agency drawn "exactly the wrong conclusion" from last week's budget agreement and shown a "stunning lack of knowledge about basic U.S. fiscal budget math."