Stock index futures were poised for a slightly lower open on Tuesday before factory orders data and after stocks had their best week in two years last week, leaving the market primed for a decline.

The Commerce Department releases May factory orders data at 10 a.m. <1400 GMT>. Economists in a Reuters survey expect a rise of 1.0 percent compared with a 1.2 percent drop in the prior month.

Equities have rallied for five straight days for a 5.6 percent gain on the S&P, rebounding from a spate of weakness over the last two months. Moves to avert a debt crisis in Europe and surprisingly strong regional business data helped lift some of the gloom on Wall Street.

We do have factory orders. The market certainly could be headed for some sort of a pullback. We've had a strong performance over the past week and any slight disappointment would invite some profit-taking, said Peter Cardillo, chief market economist at Avalon Partners in New York.

We are going to begin to see some of the data actually turn up and pointing to better times ahead in terms of the economy and certainly negating any new downward trend -- the soft patch obviously temporary.

Volume is expected to remain low in the holiday-shortened week, which could increase volatility. Markets were closed on Monday for the Independence Day holiday.

The bottom line is when you have light volume, the gyrations are going to be exaggerated on both sides of the equation, said Cardillo.

S&P 500 futures lost 3 points and were slightly below 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 gained 2 points, and Nasdaq 100 futures rose 3 points.

Specialty chemicals maker OM Group Inc is making a push into Europe with the acquisition of German magnetic materials maker Vacuumschmelze GmbH & Co KG for $993.2 million.

Southern Union Co advanced 2.4 percent to $41.60 in premarket trading after pipeline operator Energy Transfer Equity LP raised its bid to buy its rival by 21 percent to about $5 billion, trumping the $4.9 billion bid offer from Williams Companies Inc .

Immucor Inc surged 31 percent before the market's open to $27.15 after the diagnostics firm said it agreed to be acquired by private equity group TPG Capital for a fully diluted equity value of $1.97 billion.

Pfizer Inc
shed 0.4 percent to $20.67 after a study found on Monday that healthy, middle-aged smokers who take the drugmaker's Chantix or Champix, one of the most popular quit-smoking drugs, have a higher risk of suffering heart attacks or other serious heart problems.

China's Baidu is to partner with Microsoft for English-language search, giving the U.S. software giant a chance to expand its tiny Web presence in the market.

Microsoft shares gained 0.5 percent to $26.14 in premarket trading and Baidu added 2.3 percent to $146.70.

(Reporting by Chuck Mikolajczak; Editing by Kenneth Barry)