Wall Street edged lower on Friday, weighed down by energy shares as crude oil prices tumbled under pressure from a rising U.S. dollar.

Renewed worries about Greece's debt problems sent the euro to a more than two-week low against the greenback and pressured oil and other commodity prices. Crude lost almost 2 percent, and the Reuters/Jefferies commodities index <.CRB> fell 1 percent.

The dollar is very strong this morning, and that's weighing on commodity-related stocks and companies that derive a large amount of sales from overseas, said Michael Sheldon, chief market strategist at RDM Financial in Westport, Connecticut.

The Dow Jones industrial average <.DJI> dropped 26.60 points, or 0.25 percent, to 10,752.57. The Standard & Poor's 500 Index <.SPX> fell 4.78 points, or 0.41 percent, to 1,161.05. The Nasdaq Composite Index <.IXIC> lost 15.13 points, or 0.63 percent, to 2,376.15.

Palm Inc

tumbled 18.9 percent to $4.58 one day after it warned that quarterly revenues would be far below expectations.

Boeing Co rose 1.2 percent to $71.73, limiting losses on the Dow industrials, after it said it will move up production for both its 777 and 747 airliners.

Health insurer Aetna Inc rose nearly 2 percent to $33.87 after it forecast first-quarter earnings beating Wall Street predictions, but held to its previous projection for full-year profit. An index of health insurer stocks <.HMO> rose 1.6 percent.

A looming U.S. Congressional vote to overhaul the U.S. healthcare system will keep health-sector stocks in focus.

The European Union's monetary affairs chief urged the bloc's leaders to agree on a standby aid package for Greece next week, but investors fear German reluctance could hinder the effort.

Volume has been thin during the week and volatility has dropped considerably, with the CBOE Volatility Index <.VIX> down roughly 5 percent this week and hitting its lowest mark since May 2008.

Friday marks the second day of a convergence known as quadruple witching, when four types of options and futures contracts expire, possibly triggering volatility and higher volumes.

(Additional reporting by Leah Schnurr; editing by Jeffrey Benkoe)

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