Stock index futures pointed to a slightly higher open on Tuesday as earnings reports from companies including economic bellwether United Parcel Service Inc encouraged investors.

UPS, the world's largest package delivery service, reported a nearly 10 percent drop in fourth-quarter profit, but said it expected a sharp increase in earnings for 2010. The stock rose 2.3 percent to $59.72 in premarket trade. UPS is considered a bellwether because it handles so much of the nation's shipping.

Homebuilder D.R. Horton Inc posted its first quarterly profit in almost three years, helped by a large tax credit, beating estimates and sending its shares up 7.5 percent to $12.80 premarket.

The focus is going to remain on earnings, said Peter Boockvar, equity strategist at Miller Tabak & Co in New York.

People are reading through these reports to gauge the sustainability of the economic rebound that we seem to be having, and the degree of that improvement.

S&P 500 futures rose 1.9 points and were 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 gained 13 points, and Nasdaq 100 futures added 2 points.

According to the latest available Thomson Reuters data, 77 percent of the S&P 500 companies reporting so far have beaten estimates.

Investors will also eye White House adviser Paul Volcker's testimony before a Senate panel urging lawmakers to curb risks taken by large banks.

Volcker is expected to tell the Senate Banking Committee that commercial banks' proprietary and speculative activities should not be protected by the government, according to testimony obtained by Reuters. His comments could hurt bank stocks, which tumbled when reports on the proposal broke last month.

If (Volcker) backs off a little bit, or if people gain confidence (the proposal) is not going to be as pointed as it seemed when it was first announced, then maybe that will help the banks, Boockvar said.

The National Association of Realtors will issue pending home sales for December at 10 a.m. Economists expect a 1.0 percent rise, compared with a 16.0 percent fall in the previous month.

(Editing by Jeffrey Benkoe)