US STOCKS-Energy lifts Dow, S&P but credit worries remain

* Oil jumps more than $5, boosting energy stocks

* Credit jitters weigh on financial, bank shares

* Fannie, Freddie shares seesaw on bailout uncertainty

* Dow up 0.1 pct, S&P 500 up 0.3, Nasdaq off 0.4 pct (Updates to close)

By Steven C. Johnson

NEW YORK, Aug 21 (Reuters) - The Dow and S&P 500 rose on Thursday as surging oil prices drove up energy shares, though fresh fears of more credit losses on Wall Street kept gains modest and pushed the Nasdaq into negative territory.

U.S. crude oil jumped more than $5 a barrel on rising tensions between the United States and energy behemoth Russia and the weaker dollar. Shares of Exxon Mobil (XOM.N) rose 2 percent and were one of the biggest boosts on the Dow and S&P.

Bank shares struggled for much of the session as analysts predicted more mortgage-related write-downs on Wall Street.

"Oil stocks had fallen quite sharply during the decline, so there's a bit of a relief rally going on right now," said John Praveen, chief investment strategist at Prudential International Investment Advisers in Newark, New Jersey,

Crude oil had dipped below $113 a barrel earlier this month after soaring to a record high above $147 in mid-July.

The Dow Jones industrial average .DJI was up 12.62 points, or 0.11 percent, at 11,430.05. The Standard & Poor's 500 Index .SPX was up 3.17 points, or 0.25 percent, at 1,277.71. The Nasdaq Composite Index .IXIC was down 8.70 points, or 0.36 percent, at 2,380.38.

Energy shares rose with the price of oil. Chevron (CVX.N) rose 2.4 percent to $88.52 and Exxon Mobil (XOM.N) advanced 2 percent to $80.35. The Standard & Poor's Energy Index rose 2.3 percent.

Home finance giants Fannie Mae (FNM.N) and Freddie Mac (FRE.N) came back from earlier losses of about 20 percent as growing speculation of an imminent government bailout forced investors to buy back shares to exit bets on a further decline.

"Those stocks have been pounded. When they consolidated, I think you had a lot of shorts that were willing to cover," said Marc Pado, U.S. market strategist at Cantor Fitzgerald & Co in San Francisco. "People were saying, 'Let's not get too greedy here.'"

The two companies, which own or guarantee about half of outstanding U.S. mortgages, are considered a pillar of the U.S. housing market, and investors are eager to see what sort of rescue they might get from the government.

Fannie shares rose 10.2 percent to $4.85 while shares of Freddie Mac dipped 2.8 percent to $3.16.