U.S. stocks were set to open slightly higher on Monday as investors weighed a batch of acquisition activity against another climb in oil prices on unrest in the Middle East and North Africa.

Brent crude gained 1.5 percent to $117.65 a barrel and U.S. oil futures were up 2.2 percent to $106.76 as fighting in Libya disrupted the nation's oil supplies and on renewed concerns of wider disruptions in the region.

Western Digital Corp advanced 8.5 percent to $32.55 in premarket trading as the world's No. 2 computer hard drive maker agreed to buy Hitachi Ltd's <6501.T> hard disk drive operations for about $4.3 billion.

Government troops seeking to dislodge rebels from Libya's coast advanced on an oil town amid accelerating humanitarian efforts to prevent civilian suffering from worsening and a mass refugee exodus.

OPEC is contemplating whether to hold an extraordinary meeting, Qatar's Energy Minister said, who added there was no supply shortage in the market.

There is a lot out there, whether it is rising commodity prices, specifically rising energy prices, the ongoing risk associated with North Africa, you pick the country, rising rates on the stage for Trichet and the (European Central Bank), said Peter Kenny, managing director at Knight Equity Markets in Jersey City, New Jersey.

There is a lot working against the market at this stage of the game. Now any gains are going to be hard fought and are going to really have to be justified. We are well past the easy sledding.

S&P 500 futures gained 1.7 points and were slightly above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures rose 16 points, and Nasdaq 100 futures climbed 5.5 points.

In Saudi Arabia, security forces detained at least 22 minority Shi'ite Muslims who protested what they said was discrimination. The Saudi Shi'ites have staged small protests for about two weeks in the kingdom's east, site of much of the oil wealth of the world's top crude exporter.

Citigroup raised its price forecasts for Brent and West Texas intermediate crude for 2011 and 2012, in part citing a fear premium on threats of continued output disruptions.

The London Stock Exchange is eyeing a takeover of U.S. rival Nasdaq OMX Group Inc , just weeks after the London bourse announced a merger with the Toronto stock exchange, the Sunday Times reported. Nasdaq shares added 2.1 percent to $28.62 premarket.

Accuray Inc will acquire TomoTherapy Inc , a smaller rival in radiation therapy systems, for about $277 million. Accuray dipped 3 percent to $9.71, while TomoTherapy surged 28.1 percent to $4.70 premarket.

(Reporting by Chuck Mikolajczak; editing by Jeffrey Benkoe)