* Global markets pummeled by stimulus worries
* Safeway surges, to sell Canadian assets to Empire
* Retail sales data for May due
* Futures down: Dow 83 pts, S&P 4.3 pts, Nasdaq 7.5 pts
By Leah Schnurr
NEW YORK, June 13 (Reuters) - U.S. stock index futures fell on Thursday as investors continued to position themselves for the eventual winding down of central bank stimulus that has propelled the equity market rally this year.
The weakness in futures followed a slump in stocks globally. Investors are trying to gauge when central banks around the world - and particularly the Federal Reserve - will pull back on their accommodative monetary policy.
"The easy money helped us on the way up. The concern is mounting it's going to end," said Andre Bakhos, director of market analytics at Lek Securities in New York.
Comments from Fed Chairman Ben Bernanke last month stoked worries that the central bank could slow its $85 billion a month bond purchase program sooner than expected. Investors were looking to the Fed's policy-setting committee meeting next week for clarity on how soon the Fed will end its stimulus measures.
Nervousness over the withdrawal of economic support was exacerbated earlier this week when the Bank of Japan held its monetary policy steady, and investors have been unwinding some of the trades built around central bank support. The benchmark S&P 500 has advanced 13 percent so far this year.
"The action has been choppy and erratic," said Bakhos. "It's a case of investors looking to limit exposure ahead of next week's Fed meeting."
Adding to the uncertainty, the World Bank cut its outlook for global growth amid a deeper-than-expected recession in Europe and slowdown in some emerging markets. The bank forecast the world's gross domestic product will grow 2.2 percent this year, down from its previous forecast of 2.4 percent growth and slightly below last year's growth of 2.3 percent.
S&P 500 futures fell 4.3 points and were below 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 slipped 83 points, and Nasdaq 100 futures lost 7.5 points.
Among economic reports due on Thursday are those on retail sales, import prices, business inventories and weekly jobless claims.
Retail sales will likely garner the most attention, with investors hoping that consumer resilience remains intact. Sales are forecast to have risen 0.4 percent in May.
Safeway shares surged more than 25 percent after Empire said it would buy Safeway's assets in Canada for $5.7 billion. Safeway was up 25.5 percent at $29.00 in premarket trading.
Clearwire Corp's board urged shareholders to accept a tender offer from Dish Network Corp over an earlier deal with majority owner Sprint Nextel Corp to buy out the minority shareholders of the wireless service provider.
Apple Inc is exploring launching iPhones with bigger screens, as well as cheaper models in a range of colors, over the next year, sources said.