US STOCKS-Futures edge lower following Fed comments
* Ukraine in view as Russia seizes naval bases
* Jabil Circuit outlook tops expectations
* Jobless claims, housing data both on tap
* Futures down: Dow 45 pts, S&P 5.6 pts, Nasdaq 11.5 pts
By Ryan Vlastelica
NEW YORK, March 20 (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. Continuación...