* Concern about slowing stimulus hits global markets
* Safeway surges, to sell Canadian assets to Empire
* Futures down: Dow 83 pts, S&P 4.6 pts, Nasdaq 10.5 pts
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 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.
* Adding to the uncertainty, the World Bank cut its outlook for global growth, saying the economy should expand more slowly this year than last. The bank forecast the world's gross domestic product will grow 2.2 percent this year, slightly below last year's growth of 2.3 percent.
* S&P 500 futures fell 4.6 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 10.5 points.
* Among economic reports due on Thursday, investors will take in retail sales, import prices, business inventories and weekly jobless claims.
* Safeway shares surged more than 20 percent after Empire said it would buy Safeway's assets in Canada for $5.7 billion. Safeway was up 23.3 percent at $28.49 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.