US STOCKS-Wall St to dip at open as IBM results drag

* IBM (NYSE: IBM - news) slumps after quarterly results

* Apple (NasdaqGS: AAPL - news) earnings due after the close

* Futures off: Dow 99 pts, S&P 4.25 pts, Nasdaq 0.75 pt (Updates prices, adds premarket actives)

By Chuck Mikolajczak

NEW YORK, Oct 20 (Reuters) - U.S. stocks were poised for a slightly lower open on Monday, on the heels of a fourth week of losses for the benchmark S&P 500, as quarterly results from IBM disappointed.

IBM shares slumped 7.5 percent to $168.46 in premarket after the company's third-quarter earnings fell well short of Wall Street expectations. IBM had earlier said it would pay Globalfoundries $1.5 billion in cash over the next three years to take its loss-making semiconductor unit.

IBM's weakness is likely to produce an outsized drop in the Dow Jones Industrial Average, as the stocks closed out Friday's trading as the second-most expensive on the price-weighted index.

Stock index futures dropped after the IBM results, but managed to pare losses as the weak results spurred speculation the Federal Reserve may be reluctant to end its massive bond-buying stimulus program this month.

"On a number like that, with the forecast they gave you would expect the broader market would come under more pressure, and maybe it will," said Ken Polcari, Director of the NYSE floor division at O'Neil Securities in New York.

"But what it is telling you is, based on IBM's report, that the odds are lining up we may hear some more dovish comments out of the Fed next week than not."

S&P 500 e-mini futures were down 4.25 points and fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract, indicated a modestly lower open. Dow Jones industrial average e-mini futures fell 99 points and Nasdaq 100 e-mini futures shed 0.75 point.

The S&P 500 rallied on Friday to pare its weekly decline, but still notched its longest stretch of weekly losses since August 2011. The S&P index is now down 6.2 percent from its record high, hurt by worries about the health of the global economy, the spread of the Ebola virus and uncertainty about the next steps for the Federal Reserve.

Earnings season will ramp up significantly this week, with nearly 130 S&P 500 companies scheduled to report, include Apple Inc after the close on Monday.

According to Thomson Reuters data through Friday, of 81 companies in the S&P 500 that have reported quarterly earnings, 64 percent beat analyst expectations, slightly above the 63 percent average since 1994 but below the 67 percent rate for the past four quarters.

Third-quarter earnings are expected to grow 6.9 percent from a year ago, on revenue growth of 3.8 percent.

Halliburton shares advanced 3.4 percent to $54.36 before the opening bell after the world's No.2 oilfield services provider reported a 70 percent rise in net income and boosted its quarterly dividend.

(Editing by Bernadette Baum)