* 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.
* Also at 8:30 a.m., durable goods data for August is expected to show orders fell 2 percent, after rising 2.2 percent in July.
* A report on new single-family home sales at 10:00 a.m. is expected to show a 1.6 percent increase in August, slower than a 5.4 percent jump in July.
* Companies expected to report quarterly earnings on Thursday include Accenture and KB Home before the bell. Nike and Bed Bath & Beyond are schedule to report after the market closes.
* S&P 500 earnings are projected to decline 3.9 percent in the third quarter from a year ago, Thomson Reuters data shows.
* Shares of Caterpillar fell 2.4 percent to $68.50 after Axiom Capital started coverage with a “sell” rating, according to Streetinsider.com.
* Conatus Pharmaceuticals jumped 35.9 percent to $7.80 after its experimental liver cirrhosis drug met mid-stage study goals.
Futures snapshot at 7:14 a.m. ET:
* S&P 500 e-minis were down 15.5 points, or 0.8 percent, with 230,212 contracts traded.
* Nasdaq 100 e-minis were down 43 points, or 1.01 percent, on volume of 46,804 contracts.
* Dow e-minis were down 138 points, or 0.85 percent, with 39,146 contracts changing hands. (Reporting by Abhiram Nandakumar in Bengaluru; Editing by Savio D‘Souza)