U.S. stocks futures pointed to a lower open for Wall Street on Thursday, ahead of data expected to show a slowdown in durable-goods orders and testimony from Federal Reserve Chairwoman Janet Yellen.

Also casting a shadow across sentiment were an escalation in tensions in Ukraine and downbeat data out of Europe.

Building on earlier losses, futures for the Dow Jones Industrial Average fell 70 points, or 0.4%, to 16109, while those for the S&P 500 index eased 8.3 points to 1833.60. Futures for the Nasdaq-100 index also gave up a grip on gains, down 11 points, or 0.3%, to 3662.75.

A slowdown in orders over the past few months by U.S. manufacturers is likely to be reflected in the durable-goods orders reading for January, due at 8:30 a.m. EST. Economists polled by MarketWatch expect orders to drop 2.5%, after a 4.2% fall in December. Stripping out volatile autos and airlines, orders are expected to be flat or fall slightly.

Also at 8:30 a.m. EST, weekly jobless claims are due for release, and they're forecast to hold steady at around 335,000.

Markets will be keeping a close eye on Capitol Hill, with Ms. Yellen due to talk to the Senate Banking Committee about the economic outlook and monetary policy. Her appearance, delayed from earlier this month by a winter storm, is set for 10 a.m. EST.

Headlines out of Ukraine were weighing on sentiment and a market that has struggled to break through key technical levels in recent sessions. U.S. stocks finished a choppy session on Wednesday with the S&P 500 index closing flat at 1845.16. The index has topped a key technical level of 1850, just under its Jan. 15 record close, during the last three sessions, but has failed to hold above that level into the close.

Wouter Sturkenboom, London-based investment strategist at Russell Investment, said there was a clutch of European data that also didn't do much for sentiment, such as slower-than-expected Spanish economic growth.

"In general, what most people are worried about is: The year of 2014 is supposed to validate 2013, and the data right now, even though...weather is having a big impact, is not doing that. It isn't coming in strong enough to validate those rallies," Mr. Sturkenboom said. "That's what's driving markets right now, that stop-and-go behavior."

Within the geopolitical fear circle, the worry on the minds of many was potential Russian intervention in Ukraine. Earlier Thursday, armed gunmen took control of the parliament and local government offices in the Ukrainian region of Crimea and raised a Russian flag above the building. A day earlier saw a tense standoff between pro-Russian protesters and Crimean Tatars who had largely backed the opposition movement that removed President Viktor Yanukovych from power.

Mr. Yanukovych himself said Thursday that he still considers himself the legitimate leader of Ukraine, The Wall Street Journal reported.

Ukraine's acting president, Oleksandr Turchinov, said in parliament on Thursday that any movement by the Russian military in Crimea, outside the Black Sea fleet in Sevastopol, would be treated as an act of aggression. Russian President Vladimir Putin on Wednesday ordered military exercises for 150,000 Russian soldiers, some of them stationed 200 miles from the Ukrainian border.

The Russian RTS index was down over 2%, while the ruble fell 0.5% to 36.215 against the dollar. The dollar was largely firmer across the board. European stocks were also down by full percentages in some regions, with the Stoxx Europe 600 index off almost 1%. Asia stocks closed with marginal gains, mostly. Gold was higher, and oil was flat.

Best Buy Co Inc. (BBY) and Kohl's Corp. (KSS) are due to report earnings ahead of Thursday's opening.

J.C. Penney Co. (JCP) was up 14% in thin premarket trading, after making gains late Wednesday on better-than-expected results.

Tesla Motors Inc. (TSLA) was also pointing higher in premarket after the electric-car maker said it is going to build a $5 billion battery factory somewhere in the U.S. Southwest and is selling $1.6 billion in debt.