U.S. stocks fell on Wednesday on renewed worries over Greece's finances and another big Treasury debt auction.

The U.S. Treasury will auction $21 billion of 10-year notes at 1 p.m. EDT in what will be the third sizable sale of government debt this week.

The KBW bank index <.BKX>, up in the past four sessions, ticked lower, with JPMorgan Chase down 0.7 percent at $45.52.

Until they have a series of debt maturities due, any time you see Greece flaring back in the headlines, the market gets a bout of indigestion, said Kevin Kruszenski, head of listed trading at KeyBanc Capital Markets in Cleveland.

You throw Greece in on a day of an auction, you might see a bit of flight to safety, which might suggest the auction should go well.

The Dow Jones industrial average <.DJI> dropped 40.66 points, or 0.37 percent, to 10,929.33. The Standard & Poor's 500 Index <.SPX> fell 3.50 points, or 0.29 percent, to 1,185.94. The Nasdaq Composite Index <.IXIC> shed 1.97 points, or 0.08 percent, to 2,434.84.

U.S. stocks have racked up five weeks of gains, pushing major indexes to highs not seen in a year and a half.

Investors expect the 10-year Treasury note auction later today to see decent demand -- given the success of two earlier auctions this week -- and the fact that yields have risen sharply of late, making Treasury debt more attractive.

But rising yields suggest borrowing costs for the U.S. government may be on the rise, which could hamper efforts to revive the economy.

On Monday, the yield of the 10-year note, a benchmark for mortgage rates, touched 4 percent, raising concerns about the impact of rising interest rates on the housing sector. Since then, the 10-year note's yield has eased to 3.95 percent as bargain hunters bought some debt and pushed the price up slightly.

Energy shares ranked among the top decliners as crude oil prices fell after a government oil inventory report showed crude stockpiles rose last week more than forecast.

Exxon Mobil Corp , down 0,6 percent at $67.49, and Chevron Corp , down 0.3 percent at $77.65, were among the top drags on the Dow industrials.

Shares of Massey Energy , owner of the West Virginia mine where 25 miners died in an explosion this week, lost 5 percent to $46.05 after Standard & Poor's said it might cut the company's ratings.

Monsanto Co fell 1.9 percent to $68.21 after the agricultural seed company reported a quarterly profit below expectations.

The Nasdaq was supported by strength in technology stocks

such as Apple Inc , up 0.6 percent at $240.96, and Cisco Systems Inc , up 0.7 percent at $26.39.

Federal Reserve Chairman Ben Bernanke is scheduled to speak on Economic Challenges: Past, Present and Future at a Dallas luncheon at 1:30 p.m. (1730 GMT) on Wednesday. Investors will scour his comments for clues about the Fed's thinking on interest rates and the economy, given recent better-than-expected economic data.

(Reporting by Rodrigo Campos; Editing by Jan Paschal)