* Merck quarterly profit tops estimate but revenue misses
* Twitter to report earnings after market close
* EU sanctions 15 politicians, military leaders over Ukraine
* Futures up: Dow 47 pts; S&P 5.8 pts; Nasdaq 13.25 pts
Wall Street was set for a higher open on Tuesday following a batch of earnings that were better than expected.
* Merck & Co Inc shares were up 1 percent in premarket trading after results. Britain's Reckitt Benckiser Group Plc confirmed talks to buy Merck's consumer health business, the latest asset up for grabs in a wave of recent pharmaceutical deals.
* Sprint Corp shares rose 3.5 percent in premarket trading after the No. 3 U.S. mobile provider reported an increase in quarterly revenue in line with analysts' expectations, due to a new billing plan that lowered wireless expenses.
* Twitter is due to report after the market closes Tuesday.
* Archer Daniels Midland Co shares fell 2 percent in premarket trading after its first-quarter profit and sales missed Wall Street estimates.
* The Fed starts a two-day policy meeting later on Tuesday and is expected to reduce its monthly bond purchase program for the fourth time in a row and to provide guidance on when it might raise interest rates.
* In economic data, the Conference Board's consumer confidence index is due at 10:00 a.m. ET.
* The European Union imposed asset freezes and travel bans on 15 Russians and Ukrainians, including a Russian deputy prime minister, Dmitry Nikolayevich Kozak, over Moscow's action in Ukraine, but steered clear of sanctions on business leaders.
* S&P 500 e-mini futures rose 5.8 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 gained 47 points and Nasdaq 100 futures added 13.25 points.
* In Europe, stocks rose as optimism surrounding corporate earnings and mergers eclipsed the crisis in Ukraine, while rising euro zone money market rates and strong German consumer confidence supported the euro.
* The S&P 500 ended higher on Monday after a volatile session, as gains in Apple and Pfizer helped offset another round of selling in some high-growth tech shares.