NEW YORK (TheStreet) -- Stock futures were lower on Thursday as uncertainty over a Greek debt deal and anticipation ahead of a meeting of the Organization of the Petroleum Exporting Countries pressured markets. 

S&P 500 futures were down 0.5%, Dow Jones Industrial Average futures fell 0.45% and Nasdaq futures dropped 0.71%.

Initial jobless claims in the U.S. fell by 8,000 to 276,000 in the week ended May 30, hovering at 15-year lows, according to the Labor Department. Economists had expected the number of people applying for unemployment benefits to fall at a slower pace to 278,000. 

U.S. productivity in the first quarter fell by a revised 3.1% annual pace, according to the latest government data, a far steeper decline than a first estimate of 1.9%. Economists expected the measure to be revised to a 3% drop as the U.S. economy struggled with winter weather and West Coast port closures. 

European markets were selling off as a global bond rout continued. German 10-year Bund yields hit a high of 0.995% earlier in the session, while U.S. 10-year bond yields jumped to 2.37%. The bond market has been in focus since European Central Bank President Mario Draghi made comments on Wednesday that volatility would remain. 

Greece's debt negotiations appeared at a stalemate ahead of the country's repayment deadline on Friday. Greece is trying to secure additional debt relief ahead of the first of four debt payments due to the International Monetary Fund on Friday. Greece needs to repay the IMF nearly 1.6 billion euros ($1.75 billion) this month.

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Brent oil prices will likely fall to between $40 and $50 a barrel by year's end, according to former OPEC head of research Hasan Qabazard. Those comments were made ahead of Friday's OPEC meeting in which members are expected to keep production levels at record highs. West Texas Intermediate crude was hovering around $59.70 a barrel.

Dish Network (DISH) - Get DISH Network Corporation Class A Report spiked more than 4% in premarket trading on reports the company is discussing a potential merger with T-Mobile (TMUS) - Get T-Mobile US, Inc. Report. Discussions are in their early stages, according to The Wall Street Journal. T-Mobile shares added 6.5%. 

Opko Health (OPK) - Get OPKO Health, Inc. Report fell more than 6% after announcing it will acquire Bio-Reference Laboratories (BRLI) for $52.58 a share or around $1.47 billion. The all-stock deal will see Bio-Reference shareholders receive 2.75 shares of Opko for every share they hold. 

Joy Global (JOY) was slightly higher after beating analysts' estimates on its top- and bottom-lines. The company earned 59 cents a share, 4 cents higher than expected, though revenue fell 12.8% as demand for mining equipment declined. 

Costco (COST) - Get Costco Wholesale Corporation Report shares dropped nearly 1% after the warehouse retailer reported flat comparable-store sales in May. Comparable sales climbed 2% in the U.S., while international sales fell 4% due to the effects of gas prices and currency headwinds. 

J.M. Smucker

(SJM) - Get J.M. Smucker Company (SJM) Report

shares were on watch after the company reported a mixed quarter. Net income of 98 cents a share narrowly missed estimates, while revenue of $1.44 billion surged 17.1% from a year earlier. Sales saw a big boost due to its fourth-quarter acquisition of pet foods brand Big Heart.