(Adds close of U.S. markets)
* Oil prices drop to $140 a barrel level
* U.S. stocks slip on fears financial sector needs money
* Dollar reverses course as U.S. financial shares fall
By Herbert Lash
NEW YORK, July 7 (Reuters) - Wall Street closed lower on Monday after a wave of concern over mortgage providers' capital adequacy spoiled an early stocks rally triggered by a plunge in commodity prices led by oil.
In volatile trading, investors bailed out stocks after a brokerage report that Fannie Mae and Freddie Mac may need to raise more capital. The report by Lehman Brothers sparked weakness throughout the financial sector.
The dollar also at first rose but later it fell against the euro and erased gains versus the yen on the concerns over the health of the financial sector.
Crude oil fell below the $140 mark before settling down almost $4 on profit taking from last week's record high and signs that Iran may be more flexible in negotiations over its nuclear program. A wide range of commodities fell, including soy and corn, pushing the Reuters/Commodity Research Bureau index down nearly 3 percent.
U.S. government debt rallied and erased early losses as a stock reversal revived the bid for safe-haven U.S. government debt. Government debt in Europe also rose as investors pared bets the European Central Bank would raise interest rates again after last week's long-anticipated hike in euro zone rates.
U.S. banking shares plummeted to their lowest level in more than a decade after forecasts of soaring credit losses led investors to fret that next week's quarterly earnings reports could fall short of already low expectations.
Citigroup Inc <C.N>, Bank of America Corp <BAC.N> and Wachovia Corp <WB.N> were among the decliners after analysts predicted significant credit losses for large regional banks including Marshall & Ilsley Corp, <MI.N> SunTrust Banks Inc <STI.N> and Zions Bancorp <ZION.O>.
Analysts at Lehman Brothers said a pending change in U.S. accounting rules could force Fannie Mae <FNM.N> and Freddie Mac <FRE.N>, the largest providers of funding for U.S. home mortgages, to raise a combined $75 billion in fresh capital.
Even though the Lehman analysts said such an outcome was unlikely, investors were spooked.
A report from CreditSights also raised concerns about Freddie Mac, which it said could suffer greater losses as the mortgage insurance unit of Radian Group <RDN.N> could face more downgrades and force it to wind down its existing business.
"Fannie Mae and Freddie Mac are ground zero for mortgages," said Steve Persky, chief executive at Dalton Investments in Los Angeles. "They're the largest leveraged owners of mortgages out there, and that's not a good position to be in right now."
Freddie Mac fell 17.6 percent and Fannie Mae fell 16.9 percent. The KBW Bank index <.BKX>, a broad measure of the U.S. commercial banking sector reached its lowest level since 1997.
The broad market S&P 500 finished within 1 point of formal bear market territory. Bear markets are defined by a 20 percent fall from a peak.
The Dow Jones industrial average <
> fell 56.58 points, or 0.50 percent, at 11,231.96. The Standard & Poor's 500 Index <.SPX> fell 10.59 points, or 0.84 percent, at 1,252.31. The Nasdaq Composite Index < > fell 2.06 points, or 0.09 percent, at 2,243.32.Tech stocks tried to rally after Microsoft <MSFT.O> said it would be willing to reopen talks to buy all or part of the Internet company. Yahoo <YHOO.O> shares rose more than 12 percent.
The decline in oil prices initially lifted the appeal of beaten-down stocks in the wake of the market's recent sell-off, while speculation on two deals, one new and the other involving renewed talk about Microsoft and Yahoo, also buoyed stocks.
U.S. crude <CLc1> settled at $141.37 a barrel, down $3.92 and below Friday's low of $143.22. Brent crude <LCOc1> settled at $141.87 a barrel, down $2.55.
In Europe, merger speculation about Spain's Iberdrola <IBE.MC> lifted utility shares. Iberdrola rose 7.8 percent after the company's No. 2 shareholder said it saw no alternative to a merger between Iberdrola and Gas Natural <GAS.MC> of Spain.
Rivals EDF <EDF.PA>, Centrica <CNA.L> and Suez <LYOE.PA> gained between 3 percent and 5.5 percent.
Oil and gas producers were among the top performers in Europe despite falling oil prices. Traders cited a rebound from weakness last week.
"The fact that the sellers have been so persistent and there's been nothing but selling over the last six weeks means we are due a period of remission," said Mike Lenhoff, chief strategist at Brewin Dolphin.
"If on top of that, we get something like some decent news out of the commodities markets, oil in particular, that's great," he said.
The FTSEurofirst 300 index of top European shares <
> ended 1.3 percent higher at 1,178.69 points.After an initial decline, the euro rose.
"There is nothing on the FX front, everyone is looking at equity markets," said Ron Simpson, director of foreign exchange at Action Economics in Tampa, Florida. "Commodity and energy stocks have all got smashed."
The relentless march high in oil prices took a pause from a recent rally that has produced almost daily new record highs and lifted by almost 50 percent this year.
Gold fell along with other commodity prices across the board -- from metals to softs to grains -- as funds sold after returning from the long U.S. holiday weekend.
"Copper's down, silver's down, crude oil is down. Gold was holding support pretty well and when crude dropped $2.50, we dropped," said Jonathan Jossen, an independent gold trader at the COMEX division of New York Mercantile Exchange.
The benchmark 10-year U.S. Treasury note <US10YT=RR> rose 15/32 to yield 3.93 percent. The 30-year U.S. Treasury bond <US30YT=RR> gained 17/32 to yield 4.50 percent.
The dollar rose against major currencies, with the U.S. Dollar Index <.DXY> slight higher, up 0.04 percent at 72.732. Against the yen the dollar <JPY=> rose 0.30 percent at 107.13.
The euro <EUR=> rose 0.08 percent at $1.5717.
Asian stocks rose, snapping a six-day losing streak, on optimism that China's banking sector has thrived despite market turmoil.
Japan's Nikkei share average <
> finished 0.9 percent higher, its first gain after 12 straights sessions of losses. It was the longest losing streak since 1954.Shares in the Asia-Pacific region traded outside of Japan edged up 0.3 percent, according to an MSCI index <.MSCIAPJ>.
Spot gold prices <XAU=> fell $7.80 to $924.50 an ounce. (Additional reporting by Richard Leong, Gertrude Chavez-Dreyfuss, John Parry and Carole Vaporean in New York, Alex Lawler, Kirsten Donovan and Amanda Cooper in London; Editing by Richard Satran)