US STOCKS-Futures edge up but resistance seen ahead

* S&P futures trade in tight range below 1,333

* Southwest falls after planes grounded for inspection

* Futures: Dow up 15 pts; S&P up 2.5 pts; Nasdaq up 9 pts (Updates with grounding of Southwest planes, Pfizer selling unit, updates prices, comment, byline)

By Rodrigo Campos

NEW YORK, April 4 (Reuters) - U.S. stock index futures edged higher on Monday, with the S&P 500 facing a level where selling has clustered in recent sessions.

S&P 500 futures traded in a tight range below 1,333. The benchmark has been unable to close above that level since mid-February, although it was briefly pierced on Friday.

That level is double the 12-year low hit in March 2009 and is not far from 1,344, the S&P's 2011 high and its highest since June 2008.

On Friday, the S&P closed its best two-week period since December and the Dow industrials <.DJI> hit its highest intraday level since June 2008.

"The speed with which we moved up is putting a bit of a curb on a further rally," said Rick Meckler, president of investment firm LibertyView Capital Management in New York.

"Certainly there are plenty of traders who will be using this runup to try and take profits and get back at a better point. It's hard to maintain the speed of this advance," he said.

The lack of significant economic data on Monday, nuclear and other quake-related problems in Japan and unrest in Libya, Syria and other states in the oil-rich region could translate into low volumes in Wall Street. Last week was the lowest in volume so far in 2011.

S&P 500 futures rose 2.5 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures gained 15 points and Nasdaq 100 futures added 9 points.

Southwest Airlines Co shares dropped 4.7 percent in light premarket trading after planes were grounded for inspection. A U.S. safety investigator said on Sunday evidence of widespread fuselage cracks was found on a jet that made an emergency landing with a hole in the cabin. For details see [ID:nWEN0436].

In the latest M&A activity, Pfizer Inc rose 1.1 percent to $20.60 after the drugmaker agreed to sell its Capsugel unit, the world's largest maker of hard capsules, to private equity firm KKR & Co for nearly $2.4 billion.

Some nervousness over the political unrest in the Middle East and North Africa continued to linger in financial markets, with Brent crude rising to a 2-1/2 year high above $119 on the worries.

In other company news, Nasdaq OMX Group Inc and IntercontinentalExchange Inc are expected to face serious hurdles to their bid for NYSE Euronext . [ID:nN01259828].

Separately, Deutsche Boerse is holding off on making any decision as to whether to raise its rival offer for NYSE Euronext, two sources familiar with Deutsche Boerse's thinking said on Monday. [ID:nLDE7330LT]. Shares of NYSE Euronext dipped 1.5 percent in light premarket trading.

The U.S. Bureau of Ocean Energy Management said on Sunday it had not struck a deal with BP to allow the oil company to resume deep-water drilling in the Gulf of Mexico, refuting a press report. [ID:nN03212134]. (Reporting by Rodrigo Campos; Editing by Kenneth Barry)