* Positive German, Chinese data outweighed by Fed uncertainty
* Fed's Dudley says Fed could begin tapering stimulus this year
* Apple shares jump after most successful iPhone launch ever
* Indexes down: Dow 0.2 pct, S&P 0.3 pct, Nasdaq 0.1 pct
By Caroline Valetkevitch
NEW YORK, Sept 23 (Reuters) - U.S. stocks fell on Monday, putting the S&P 500 on track for a third session of declines, weighed down by a Federal Reserve official's comments and a looming political deadline in Washington.
William Dudley, president of the Federal Reserve Bank of New York, said on Monday that the timeline that Fed Chairman Ben Bernanke articulated in June for scaling back the central bank's stimulus measures is "still very much intact," as long as the economy keeps improving.
Citigroup led the S&P financial sector lower, a day after the Financial Times reported Citi had a significant drop in trading revenue during the third quarter, which could hurt the bank's earnings. Citi shares fell 3.1 percent to $49.63 and the S&P financial index lost 1.4.
Investors were caught off guard last week when the Fed decided against reducing asset purchases from the current $85-billion monthly pace, after many had anticipated a change in policy in September.
The S&P 500 had rallied 1.2 percent last Wednesday after the decision by the Fed. But the index is now on pace for a third straight day of declines.
Adding to concerns was the approaching Oct 1 deadline for Congress to avoid a government shutdown as lawmakers negotiate ahead of the end of the fiscal year on Sept. 30.
"I think investors are a little more concerned about the debate going on in Washington and the volatility that may create over the next few weeks," said Michael Sheldon, chief market strategist of RDM Financial in Westport, Connecticut.
The Dow Jones industrial average was down 30.97 points, or 0.20 percent, at 15,420.12. The Standard & Poor's 500 Index was down 5.63 points, or 0.33 percent, at 1,704.28. The Nasdaq Composite Index was down 3.33 points, or 0.09 percent, at 3,771.40.
U.S.-listed shares of Blackberry were up 1.3 percent at $8.85 after a consortium led by Fairfax Financial offered to buy the Canadian smartphone maker for $4.7 billion. Shares were down earlier in the day.
Blackberry announced Friday a change in focus away from the consumer in favor of businesses and governments. The move added to fears about BlackBerry's long-term viability.
Among positives for the market, a flood of new orders gave a boost to European and Chinese firms in September, according to surveys that added to evidence that the global economy is healing, but U.S. factory activity lost some momentum.
Apple shares were a bright spot, up 4.6 percent to $488.69, after it said it sold 9 million iPhone 5s and iPhone 5c models since their launch on Friday.
The widely followed Dow Jones industrial average started Monday with three new components. Goldman Sachs, Visa and Nike replace Bank of America, Hewlett-Packard and Alcoa.
Shares of Goldman, Visa and Nike and HP all declined Monday while Alcoa edged higher and Bank of America fell with the financial sector.