By Chuck Mikolajczak

NEW YORK (Reuters) - Stock futures advanced on Thursday, indicating stocks may rebound after two straight days of declines, ahead of data on the labor market.

The S&P 500 <.spx> dropped more than 1 percent Wednesday and has lost 1.9 percent over the past two sessions as concerns mounted that the Federal Reserve may scale back its bond-buying stimulus before the economy is strong enough to stand on its own.</.spx>

The two-day drop for the benchmark S&P index is the worst back-to-back performance since a 2.1 percent decline in mid-April.

Investors will eye weekly initial jobless claims data at 8:30 a.m. EDT (1230 GMT) for clues on the health of the labor market ahead of Friday's important payrolls report. Economists in a Reuters survey forecast a total of 345,000 new filings compared with 354,000 in the prior week.

The S&P 500 had run up to a record high on May 21, partly fueled by the belief that softer economic data would ensure the Fed would keep its stimulus measures in place, as opposed to scaling them back earlier than expected.

"There is no question, the market is not responding to 'bad news is good news, good news is bad news,'" said Peter Cardillo, chief market economist at Rockwell Global Capital in New York.

"The focus now is if the economy continues to slip and the global economy continues to slip, then that could impact earnings but that probably will wane after tomorrow's employment data."

Wednesday's ADP National Employment report showed private employers accelerated hiring in May from the prior month, but the gains fell short of expectations.

S&P 500 futures rose 7.6 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures added 50 points, and Nasdaq 100 futures gained 10 points.

SodaStream International jumped 7.1 percent to $74.30 in premarket trading after the Calcalist financial newspaper said PepsiCo Inc is in talks to buy the maker of home beverage systems for $2 billion. CNBC later cited an email from PepsiCo's chief executive calling the reported offer "untrue."

Retailers will also be eyed as they report monthly sales results. Costco Wholesale Corp reported May same-store sales that missed analyst estimates, due to a relatively stronger dollar and weak gasoline prices.

Ciena Corp shares climbed 9.4 percent to $17.85 after the network equipment maker posted a surprise rise in adjusted quarterly profit, helped by a 3 percent increase in its gross margin.

Vera Bradley Inc shares slumped 9.6 percent to $20.30 before the opening bell after the women's fashion company reported second-quarter results and said Chief Executive Michael C. Ray planned to retire from the company.

In Europe, Johnson Matthey was the star performer after results as the chemicals firm led European shares slightly higher, with trading expected to remain volatile ahead of the U.S. economic data. <.eu></.eu>

Asian shares tumbled to fresh 2013 lows as growing uncertainty on whether the U.S. Federal Reserve would roll back its stimulus this year kept markets on edge.

(Editing by Bernadette Baum)