* Futures down: Dow 20 pts, S&P 3.75 pts, Nasdaq 7.25 pts
By Tanya Agrawal
Sept 23 (Reuters) - U.S. stock index futures were slightly lower on Friday as oil prices came off a two-week high, a day after the Nasdaq closed at a record high for the second straight day.
* All three major indexes are poised to end the week higher after the S&P 500 index notched its best two-day performance in more than two months on Thursday. The S&P is up 6.5 percent for the year.
* Investors have been in risk-on mode again, encouraged by the Federal Reserve's decision to stand pat on interest rates at a meeting this week.
* Fed Chair Janet Yellen said on Wednesday that U.S. growth was looking stronger and rate increases would be needed to keep the economy from overheating and fueling high inflation. But the central bank maintained the low-interest rate environment that has helped underpin the bull market for stocks.
* The U.S. central bank had hinted that it might raise rates before the year ends and interest rate futures were pricing in roughly a 60 percent chance of a rate increase by December.
* Oil prices fell on Friday, following two sessions of strong rises, on caution ahead of a gathering of OPEC ministers next week in Algeria to discuss possible production cooperation to rein in global oversupply.
* Investors will also keep an eye on a number of Fed speakers who are scheduled to speak at different events for further clues regarding the timing of the next rate hike.
* Fed speakers include Dallas Federal Reserve Bank President Robert Kaplan, Philadelphia Fed President Patrick Harker, Cleveland Fed President Loretta Mester and Atlanta Fed President Dennis Lockhart.
* Twitter shares were down 4.2 percent at $17.84 in premarket trading after RBC cut its rating on the stock to "underperform".
* Yahoo was down 2.4 percent at $43.05, a day after the company said at least 500 million of its accounts were hacked in 2014 in a theft that appeared to be the world's biggest known cyber breach.
Futures snapshot at 6:58 a.m. ET (1058 GMT):
* S&P 500 e-minis were down 3.75 points, or 0.17 percent, with 97,617 contracts traded.
* Nasdaq 100 e-minis were down 7.25 points, or 0.15 percent, on volume of 16,097 contracts.
* Dow e-minis were down 20 points, or 0.11 percent, with 13,008 contracts changing hands. (Reporting by Tanya Agrawal; Editing by Don Sebastian)