* Fed officials' remarks spur uncertainty over stimulus pullback
* S&P 500 falls under its 14-day moving average
* Walt Disney drags on Dow after results
* Indexes down: Dow 0.36 pct; S&P 0.37 pct; Nasdaq 0.38 pct
By Chuck Mikolajczak
NEW YORK, Aug 7 (Reuters) - U.S. stocks fell for a third straight day on Wednesday on growing uncertainty over when the Federal Reserve may start to wind down its stimulus, which has been a major force behind the run higher in equities this year.
Even after the benchmark S&P index suffered its biggest decline since June 24 on Tuesday, the market was unable to shake off comments from a pair of Fed officials that muddied the water over how soon the central bank might reduce its bond-buying program.
The S&P 500 broke below 1,694.03 on Wednesday, its 14-day moving average that had served as a support level. The broad market index is down about 1.4 percent for the week, on track for the worst weekly performance since a 2.1 percent decline the week of June 21 in the wake of the last Fed policy meeting.
However, the index is still is still up 18.6 percent this year after climbing to a record high on Friday.
"People were concerned about the extent of the rally in the short term, and some people are talking about equities being too expensive relative to the underlying fundamentals," said Stephen Massocca, managing director at Wedbush Equity Management LLC in San Francisco.
"And of course, the big story, the next big piece of news one would think is the taper tantrum."
In the latest comment from Fed officials, Federal Reserve Bank of Cleveland President Sandra Pianalto said the central bank would be prepared to scale back asset purchases if the labor market remains on the stronger path followed since last fall.
The Dow Jones industrial average fell 56.54 points or 0.36 percent, to 15,462.2, the S&P 500 lost 6.33 points or 0.37 percent, to 1,691.04 and the Nasdaq Composite dropped 13.976 points or 0.38 percent, to 3,651.794.
Walt Disney Co was among the biggest drags on the blue-chip Dow Jones industrial average index. The stock fell 1.7 percent to $65.90 after projecting a massive loss related to its film "The Lone Ranger" on Tuesday, though adjusted earnings slightly beat expectations.
First Solar Inc plunged 12.7 percent to $40.80 after it reported results Tuesday below expectations and cut its full-year outlook.
Ralph Lauren Corp fell 6.6 percent to $177.04 as profits declined. Both companies were among the S&P 500's biggest percentage decliners.
Equity markets have been closely tethered to central bank policy, with many investors concerned that economic growth isn't robust enough to boost markets without the Fed's help. Last week, the July payroll report came in much weaker than expected.
Chicago Fed President Charles Evans said Tuesday the Fed would probably scale back its bond-buying program later this year, perhaps beginning as early as next month, depending on economic data.
That echoed earlier comments by Dennis Lockhart, president of the Federal Reserve Bank of Atlanta, though he told Market News International the Fed might continue its stimulus program if growth doesn't meet its targets.
Through Wednesday morning, of the 434 companies in the S&P 500 that had reported earnings, Thomson Reuters data showed that 66.8 percent topped analysts' expectations, in line with the 67 percent beat rate over the past four quarters. On the revenue side, 54.1 percent have reported revenue above estimates, more than in the past four quarters, but below the 61 percent average since 2002.