By Ryan Vlastelica
NEW YORK (Reuters) - U.S. stock index futures were lower on Thursday as investors continued to digest recent comments from Federal Reserve Chair Janet Yellen, who raised the specter of an earlier-than-expected rate hike.
Wall Street fell on Wednesday, snapping a two-day advance that had taken the S&P 500 near record levels, after the central bank made clear that it would rely on a wide range of measures in deciding when to raise interest rates, dropping the unemployment rate as its definitive metric.
Yellen said the "considerable period" between the end of the Fed's bond-buying stimulus program and the first rate increase from the central bank could be six months. Many analysts had been expecting the first increase to come in the second half of 2015.
Geopolitical concerns also continued to weigh on sentiment as Russian troops seized two Ukrainian naval bases, including a headquarters in the Crimean port of Sevastopol. The United States warned Russia that it was on a "dark path" to isolation in the biggest crisis between the two countries since the Cold War.
While few U.S. companies have outsized exposure to the region, investors are concerned about the fallout to any escalation in tension.
S&P 500 futures fell 5.6 points and were below 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 fell 45 points and Nasdaq 100 futures fell 11.5 points.
The S&P 500 is within 1 percent of its record closing high, though volume has been anemic on positive market days, suggesting limited conviction behind the move.
Volume is expected to surge on Friday as options expiration takes place alongside multiple index rebalances. Credit Suisse estimates $14 billion in gross trading will stem from the S&P 500 index rebalance, with another $6 billion coming from rebalancing in other indexes.
Investors are also looking ahead to the latest economic data, with weekly jobless claims on tap for release at 8:30 a.m. (1230 GMT) Claims are seen rising by 10,000 to 325,000.
February existing home sales and the March business activity index from the Philadelphia Federal Reserve are both scheduled for release at 10 a.m. Both are seen rebounding from weakness in the previous month.
Jabil Circuit Inc
Deutsche Bank
U.S. shares of GlaxoSmithKline
(Editing by)