U.S. stocks open lower amid worries about Greece

U.S. stocks opened lower on Thursday, as lack of resolution on Greece debt talks weighed on Wall Street sentiment.

U.S. stocks bounced back from Tuesday' s sell-off on Wednesday, with the Nasdaq Composite Index setting its third closing record for 2015, boosted by improvement in the Greek debt crisis.

Greek Prime Minister Alexis Tsipras expressed optimism Wednesday that Greece and its creditors were close to reaching a deal on the future handling of the Greek debt crisis after four months of tough negotiations.

However, European officials denied a deal was near, saying the two sides still had some way to go before any agreement could be concluded and they were surprised by Athens' upbeat tone.

On economic front, in the week ending May 23, the advance figure for seasonally adjusted initial claims was 282,000, an increase of 7,000 from the previous week' s revised level, the U.S. Labor Department said Thursday.

In corporate news, Costco reported quarterly earnings of 1.17 U.S. dollar per diluted share, above estimates, though revenue and comparable store sales were below forecasts. Analysts said the warehouse retailer faced headwinds from lower gas prices and a stronger dollar.

Shortly after the opening bell, the Dow Jones Industrial Average was down 63.76 points, or 0.35 percent, to 18,099.23. The S&P 500 shed 3.14 points, or 0.15 percent, to 2,120.34. The Nasdaq Composite Index lost 5.02 points, or 0.10 percent, to 5,101.58. Endi