* Russia has 20,000 troops on Ukraine border -NATO
* Sprint, T-Mobile shares fall as Sprint drops bid
* Cognizant, Groupon shares down after results
* Futures off: Dow 63 pts, S&P 8 pts, Nasdaq 25 pts (Updates prices, adds byline)
By Rodrigo Campos
NEW YORK, Aug 6 (Reuters) - U.S. stocks were poised to fall at the open Wednesday on worries of an escalation of the conflict in Ukraine and after several key merger and acquisition deals fell through.
* NATO said Wednesday Russia has amassed around 20,000 combat-ready troops on Ukraine's eastern border and could use the pretext of a humanitarian or peace-keeping mission to invade.
* A further souring of relations between Russia and the West could hurt the European economy, already struggling to recover from a deep recession. Data on Wednesday showed German industrial orders dropped in June at their steepest rate since September 2011 and Italy's economy unexpectedly slid back into recession in the second quarter.
* Sprint dropped its bid for carrier T-Mobile U.S. after continued regulatory resistance despite months of lobbying. Sprint shares fell 17.5 percent and T-Mobile dropped 8.6 percent in heavy trading before the opening bell.
* Rupert Murdoch's Twenty-First Century Fox pulled its $80 billion offer to buy Time Warner Inc that would have created one of the world's largest media conglomerates. TWX shares slid 12.4 percent in premarket despite reporting better-than-expected results, while Fox rose 5.9 percent.
* S&P 500 e-mini futures were down 8 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 lower open. Dow Jones industrial average e-mini futures fell 63 points and Nasdaq 100 e-mini futures lost 25 points.
* Walgreen Co shares fell 15.1 percent in premarket trading after it said it wouldn't use a full takeover of Europe's biggest pharmacy chain Alliance Boots to move its domicile overseas, following fierce criticism of such tax-cutting deals at home.
* Shares of Cognizant Technology fell 13.5 percent in premarket trading after the IT services provider said it expected slower full-year sales growth than previously forecast.
* Groupon shares tumbled 17.2 percent in premarket trading a day after it slashed its full-year profit outlook. (Editing by Bernadette Baum)