YAHOO [BRIEFING.COM]: After holding above key technical levels midway through the session, the S&P 500 rolled over and violated its 200-day moving average amid broad-based selling pressure. In turn, stocks finished near session lows and the S&P 500 closed below its 200-day moving average for the third time in the past 26 sessions.

The afternoon sell-off was generally an extension of the market's recent weakness, which became more recognizable following last week's disappointing jobs report. Buyers are also showing reluctance ahead of earnings season, which unofficially begins when Alcoa (AA 9.41, +0.15) announces its latest results after Wednesday's closing bell. Alcoa won favor ahead of the report amid reports today that the company is optimistic about demand. The comments came despite persistent macro headwinds.

Concern that economic conditions remain tenuous led President Obama to indicate that a second fiscal stimulus isn't off the table. However, Dow Jones reported that Senate Majority Leader Reid doesn't believe there is any case at this stage for another economic stimulus package.

Meanwhile, the government is expected to unveil its Public-Private Investment Plan (PPIP) tomorrow. According to news sources, BlackRock (BLK 162.17, -4.06), which is the largest money manager by assets under management, will be one of the PPIP managers.

Losses were steep and broad-based as all 10 major sectors in the S&P 500 finished lower. Industrials suffered the largest blow by dropping 3.3%.

Energy was a laggard for the entire session and finished 2.5% lower as falling oil prices undercut the sector. Crude oil futures closed 1.8% lower at $62.90 per barrel, which marks the fifth straight decline and the lowest closing price for pit trading in more than one month. Still, crude oil prices are up 40% year-to-date.

Weakness among other commodities caused the CRB Commodity Index to shed 1.5%. The CRB is down nearly 4% so far this week. According to The Wall Street Journal, the U.S. Commodity Futures Trading Commission will hold hearings this summer to consider imposing position limits for commodities of finite supply. That would include oil and natural gas.

Despite succumbing to selling pressure, health care was able to limit its losses. The sector closed roughly 0.3% lower after spending nearly all of the session trading with a gain. The relative strength followed reports that hospitals have agreed to contribute funds toward covering the uninsured in the future. The agreement removes an element of uncertainty from the sector amid ongoing efforts to reform health care.

Large-cap tech issues weighed on the Nasdaq for the second straight session and caused the tech-rich index to underperform its counterparts. Semiconductors failed to provide support and shed 2.9% instead. Their decline came despite analyst upgrades for shares of Marvell Tech (MRVL 11.50, +0.10) and Intel (INTC 16.25, -0.29).DJ30 -161.27 NASDAQ -41.23 NQ100 -2.5% R2K -2.0% SP400 -2.2% SP500 -17.69 NASDAQ Adv/Vol/Dec 643/2.06 bln/2004 NYSE Adv/Vol/Dec 660/1.11 bln/2351