US Markets

US stock futures hit by Russia, Ukraine concerns

U.S. stock-index futures traded down on Wednesday, as European shares fell sharply on rising concerns about Russia and Ukraine.

Time Warner declined after Rupert Murdoch's 21st Century Fox rescinded its offer for the company. Walgreen fell after the drugstore operator said it would acquire the remaining shares in Alliance Boots that it doesn't already hold for $5.29 billion in cash and $10 billion in stock.

Read MoreWalgreen confirms Boots takeover in non-inversion deal

Stock futures cut losses some after a report had the U.S. trade deficit coming in at a less-than-expected $41.5 billion in June.

Heavy fighting has erupted in the Ukrainian city of Donetsk, as government forces try to take the area back from pro-Russian separatists. Poland's foreign minister warned on Tuesday that Russia was amassing battalion groups at the Ukrainian border.

"If Poland is indeed right that Russia is about to increase its presence in the east of Ukraine, buyers of all things risk will disappear fast as this is an undefinable event with an undefinable outcome for markets," said Evan Lucas, market strategist at IG, in a research note.

There were also concerns Russia could retaliate against the sanctions enforced by the U.S. and Europe. A Russian business newspaper reported on Tuesday that Russia was considering banning European airlines flying through Russia airspace.

Moscow has also begun to target iconic Western food brands. On July 28 it launched investigation of cheese used at McDonald's restaurants, and this Tuesday it announced a ban on U.S. bourbon due to sanitary concerns.

Stock watch

This comes after Twenty-First Century Fox withdrew its $80 billion bid for Time Warner late on Tuesday and instead authorized a $6 billion repurchase of its Class A shares. Fox will also post earnings on Wednesday, after the close of trade.

Investors should keep an eye on shares of Walgreen, which announced a $10 billion deal to buy its remaining stake in U.K. drugstore chain Alliance Boots on Wednesday morning.

Also on Wednesday morning, Walgreen posted earnings per share of 91 cents, up on earnings 85 cents in the year-ago quarter. Quarterly sales increased 5.9 percent over year-ago quarter to $19.4 billion.

Shares in Walt Disney Co. wavered in after-hours trading after it reported quarterly earnings and revenue that beat analysts' expectations late on Tuesday. CEO Bob Iger told CNBC he would not consider a tax inversion deal, even though Disney pays a high rate of corporate tax.

Sprint is abandoning its pursuit of T-Mobile US—which would have created a U.S.rival to Verizon—as the regulatory challenges of the deal are said to be too steep. This comes one day after the U.S. telecoms group rejected a rivalbid from France's Iliad.

Amazon said on Wednesday that it was expanding its same-day delivery to six more cities—Baltimore, Dallas, Indianapolis, New York City, Philadelphia and Washington DC.

Apple shares will be worth watching, after Samsung Electronics announced it was dropping all patent lawsuits with the tech giant outside the U.S.