* Fed policy statement due at 2:00 p.m. (1800 GMT)
* Adobe, FedEx higher in premarket after earnings
* ConAgra slumps after cutting outlook
* Futures: Dow off 6 pts, S&P off 0.25 pts, Nasdaq up 4 pts (Adds data, updates prices)
By Chuck Mikolajczak
NEW YORK, June 18 (Reuters) - U.S. stocks were poised for a flat open on Wednesday, after a three-day winning streak for the S&P 500 index and ahead of a monetary policy announcement by the Federal Reserve.
* The Fed is widely expected to announce another $10 billion cut to its monthly bond purchases as it wraps up a two-day policy meeting at 2:00 p.m. (1800 GMT), but is likely to make few, if any, other concrete policy moves. Investors will be attuned to whether officials may tip their hand on longer-term plans for interest rates.
* The benchmark S&P index has risen 0.6 percent over the last three days, as investors largely shrugged off mounting tensions in Iraq amid a flurry of merger and acquisition activity and better-than-anticipated manufacturing data.
* Saudi Arabia said on Wednesday Iraq faced the threat of full-scale civil war with grave consequences for the wider region and, in an apparent message to arch rival Iran, warned against outside powers intervening in the conflict.
* S&P 500 e-mini futures were off 0.25 points and fair value - a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract - indicated a flat open. Dow Jones industrial average e-mini futures fell 6 points and Nasdaq 100 e-mini futures added 4 points.
* The U.S. current account deficit widened to $111.2 billion in the first quarter, its widest point in 1-1/2 years, from a revised $87.3 billion deficit in the fourth quarter as exports slumped and the surplus on primary income declined.
* Adobe Systems jumped 8.5 percent to $73.26 in premarket trading after the maker of Photoshop and Acrobat software reported better-than-expected quarterly profit and revenue.
* FedEx Corp rose 3.6 percent to $145.31 in premarket trading after the world's No. 2 package delivery reported a better-than-expected rise in quarterly revenue on higher volumes in its ground business.
* But ConAgra Foods slumped 6.2 percent to $30.83 after the maker of Hunt's tomato ketchup and Slim Jim beef jerky said its adjusted fourth-quarter profit would be lower than expected.
* Endocyte Inc plunged 17.6 percent to $6.36 before the opening bell after the company said a Merck subsidiary would no longer pursue development of Endocyte's cancer drug, vintafolide. (Editing by Bernadette Baum)