US STOCKS-Futures fall sharply; Yellen speech awaited
* Futures down: Dow 138 pts, S&P 16 pts, Nasdaq 43 pts
By Abhiram Nandakumar
Sept 24 (Reuters) - U.S. stock index futures fell sharply on Thursday as concerns about global economic growth grew and ahead of a speech by Federal Reserve Chair Janet Yellen.
* Investors will look for clues regarding the timing of an interest rate hike when Yellen delivers a speech on inflation, a topic that is key to liftoff and one that has divided policymakers. The speech is at 5 p.m. ET (2100 GMT).
* U.S. stocks closed slightly lower on Wednesday, as weak factory data from China and the United States led to a selloff in materials and industrial stocks.
* Seeking to warm bilateral ties and project a sunny climate for U.S. business, Chinese President Xi Jinping vowed on Wednesday to cut restrictions on foreign investment.
* The U.S. equity market has been skittish since last Thursday when the Fed held off from raising rates, as was expected by some. The S&P 500 has fallen 2.8 percent since then.
* The market has already had a volatile month as concerns regarding a slowing Chinese economy and uncertainty regarding the timing of a Fed rate hike have caused sharp swings.
* U.S. economic data expected on Thursday includes weekly jobless claims, which is expected to have risen by 7,000 to 271,000. The data is due at 8:30 a.m. Continuación...