US STOCKS-S&P 500 ends flat; Fed sees risks but unlikely to reverse course

* Fed not likely to reverse course on rates despite risks

* Disney's 3.8 pct drop weighs on Dow

* Indexes: Dow down 0.6 pct, S&P down 0.02 pct, Nasdaq (NasdaqGS: NDAQ - news) up 0.4 pct (Updates close with Cisco up, Twitter (Swiss: TWTR.SW - news) down after the bell; latest volume)

By Caroline Valetkevitch

Feb 10 (Reuters) - The S&P 500 ended flat on Wednesday, losing gains late in the session as investors digested comments by Federal Reserve Chair Janet Yellen, who kept options open for more rate hikes but also saw risks to the U.S (Other OTC: UBGXF - news) . economy.

The Dow and S&P 500 posted their fourth straight day of losses while the Nasdaq ended its three-day down streak.

Materials and energy shares were Wednesday's biggest losers following further losses in U.S. oil prices.

The market had traded higher for much of the session after Yellen told Congress she does not expect the central bank to reverse the rate hike program it began in December. But Yellen also acknowledged tightening financial conditions and uncertainty about China.

"The market was strong (early in the day) because Janet Yellen confirmed the fact the Fed would go very slow on rate hikes because the economy was showing some signs of sluggishness," said Peter Tuz, president of Chase Investment Counsel in Charlottesville, Virginia.

"But maybe she is saying the economy is slower than most of us were thinking."

Investors have all but ruled out further interest rate hikes this year, after the Fed raised its fed funds rate for the first time in a decade in December.

The Dow Jones industrial average closed down 99.64 points, or 0.62 percent, to 15,914.74, the S&P 500 lost 0.35 points, or 0.02 percent, to 1,851.86 and the Nasdaq Composite added 14.83 points, or 0.35 percent, to 4,283.59.

U.S. stocks have struggled since the start of the year amid mounting worries over a slowdown in global and U.S. economic growth. The Dow and S&P 500 are down about 9 percent each so far in 2016 while the Nasdaq has lost about 14 percent.

"As long as we can avoid a recession, this correction will probably work itself out, and we'll have the opportunity to bounce back," said Kelly Bogdanov, portfolio analyst at RBC Wealth Management in San Francisco.

Walt Disney shares dropped 3.8 percent to $88.85, and were the biggest drag on the Dow. Disney dropped after reporting lower profit at its ESPN sports network.

Technology and healthcare shares rebounded from recent losses, however. The S&P technology index rose 0.4 percent while healthcare gained 0.9 percent.

After the bell, Twitter shares eased 1.8 percent to $14.70 in volatile trading after it said average monthly active users stalled in the fourth quarter, while Cisco Systems (Xetra: 878841 - news) rose 7.3 percent to $24.15 after it reported a profit that beat estimates.

During the session, advancing issues outnumbered declining ones on the NYSE by 1,646 to 1,429, for a 1.15-to-1 ratio on the upside; on the Nasdaq, 1,390 issues rose and 1,382 fell for a 1.01-to-1 ratio favoring advancers.

The S&P 500 posted 6 new 52-week highs and 22 new lows; the Nasdaq recorded 4 new highs and 208 new lows.

About 9.1 billion shares changed hands on U.S. exchanges, compared with the 9.6 billion daily average for the past 20 trading days, according to Thomson Reuters (Dusseldorf: TOC.DU - news) data. (Editing by Nick Zieminski and Meredith Mazzilli)