Stocks were set to open slightly higher on Thursday, adding to gains from the previous session, with futures for the Dow Jones, the S&P 500 and the Nasdaq all up by around 0.1 percent by 0900 GMT (4 a.m. ET).

The S&P 500 <.SPX> is heading for its best December in nearly two decades. The index has gained 6.7 percent so far this month and rose in 17 of the last 20 sessions.

Volumes, however, were expected to remain thin due to the year-end holiday period.

The Chicago Purchasing Managers Index (PMI), due at 1445 GMT (9:45 a.m. ET), is likely to give the market some direction.

The index has been running hotter than most other manufacturing indicators but the gap is expected to have narrowed a bit in the December reading, with analysts forecasting a drop to 61.0 from 62.5 the month before.

Other data likely to be closely watched include pending home sales for November, which is expected to show a slight dip, and weekly jobless claims which is seen extending a seasonal slide heading into the last week of December.

In company news, U.S. health regulators have approved Endo Pharmaceuticals Holding Inc and ProStrakan Group PLC's

Fortesta testosterone gel to treat men with low levels of the hormone.

Lockheed Martin Corp and the U.S. unit of Australia's Austal Ltd won U.S. Navy contracts potentially worth more than $3.5 billion each to design and build up to a combined total of 20 coastal combat ships through 2015.

A blizzard in the U.S. Northeast this weekend postponed about $1 billion in holiday retail sales by keeping shoppers away from stores in the days after Christmas, research firm ShopperTrak said.

In Europe, the pan-European FTSEurofirst 300 <.FTEU3> index of top shares was slightly weaker in early trade, pausing for breath following a rally in December which has put equities on track to post their biggest monthly rise in 17 months.

(Reporting by Harpreet Bhal; Editing by Mike Nesbit)