* Fed announcement expected at 2 p.m. ET (1800 GMT)
* Yellen speaks half an hour later
* Fed fund futures see 30 pct chance of hike on Thursday
* Cablevision jumps after Altice deal
* Futures down: Dow 38 pts, S&P 5.25 pts, Nasdaq 9.25 pts (Adds details, comment, updates prices)
By Tanya Agrawal
Sept 17 (Reuters) - U.S. stock index futures extended their losses ahead of the Federal Reserve's interest rate decision later on Thursday.
The Fed will announce the outcome of its policy meeting and release its latest economic projections at 2 p.m. ET (1800 GMT), followed by a news conference by Chair Janet Yellen at 2:30 p.m.
An increase in the Fed's benchmark rate, which has been near zero since the depths of the financial crisis in December 2008, would be the first since 2006.
The low rates have helped nurse the economy back to health since the crisis and underpinned a spectacular bull run for stocks.
Fed fund futures <0#FF:> indicate a 30 percent chance the central bank will raise rates on Thursday, while 35 of 80 economists polled by Reuters expect a move.
"Investors are in wait-and-see mode," said Art Hogan, chief market strategist at Wunderlich Securities in New York.
Any reaction to whatever the Fed does on Thursday is likely to be short-lived, he said.
"The real reaction is going to be felt in the coming weeks as we look at corporate earnings, economic activity and other factors."
Whether or not the Fed raises rates on Thursday, investors will be hanging on every word during Yellen's news conference.
If the Fed does not move, the focus will shift to its next meeting on Oct. 27-28.
Uncertainty about when the Fed will switch gears has dogged Wall Street for months - a situation that has been complicated in recent weeks by market turbulence linked to slowing growth in China and worries about the health of the global economy.
However, many analysts say a rate hike now would at least remove a lot of the uncertainty that has troubled investors.
Energy stocks pushed Wall Street higher on Wednesday after an almost 6-percent jump in oil prices, but trading was thin. Oil prices were a little weaker on Thursday.
"As it stands now considering (Wednesday's) market rally, the bearish decision will be for the Fed not to hike," Mike O'Rourke, chief market strategist at Jones Trading, said in a note.
S&P 500 e-minis were down 5.25 points, or 0.26 percent, with 150,209 contracts traded by 7:55 a.m. ET. Nasdaq 100 e-minis were down 9.25 points, or 0.21 percent, on volume of 16,421 contracts, while Dow e-minis were down 38 points, or 0.23 percent, with 14,039 contracts exchanged.
The Fed has said it will raise rates when it sees a sustained recovery in the economy.
Shares of Cablevision jumped 16.7 percent to $33.30 in premarket trading after European telecoms group Altice agreed to buy the company in a deal valued at $17.7 billion.
Oracle was down 2.4 percent at $37.35 a day after the company warned that revenue could fall in the current quarter. (Reporting by Tanya Agrawal; Editing by Ted Kerr)