Stock index futures were slightly higher on Thursday, a day after the S&P 500 closed at a 29-month high as several bellwether companies reported strong results.

Three Dow components posted quarterly results early Thursday, including Procter & Gamble Co
, AT&T Inc and Caterpillar Inc .

Heavy machinery maker Caterpillar climbed 2.6 percent to $98.27 before the bell after its profit topped consensus expectations.

Profits at AT&T and P&G also beat estimates, but fell from a year ago. AT&T's wireless subscriber growth was below the consensus view.

AT&T fell 2.9 percent to $27.91 premarket, while P&G lost 2.8 percent to $64.24.

The results from these major companies look pretty good, and that gives us a clue as to what we can expect in the first half of 2011, said Kim Caughey Forrest, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh.

Overseas, ratings agency Standard & Poor's cut Japan's long-term debt rating by one notch to AA minus, saying the government lacked a coherent plan to tackle its mounting debt.

A lot of people didn't believe that a country with as big an export base as Japan could be downgraded, and this is complicating the whole story line of how we should handle our own debt situation, Caughey Forrest said.

S&P 500 futures rose 1.5 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 added 22 points, and Nasdaq 100 futures rose 5 point.

Initial jobless claims are seen rising to 405,000 in the latest week, an increase of 1,000 from the previous week. Data on December durable goods, which are seen rising, is also expected. December pending home sales data will come later in the morning.

A pair of Nasdaq stalwarts will report results after the bell. Microsoft Corp is seen posting a dip in profit, while Inc is expected to report impressive fourth-quarter sales.

On Wednesday, gains in technology and commodity shares helped lift markets as investors largely ignored the U.S. Federal Reserve's lukewarm assessment of the economy. The Dow hit the 12,000 level for the first time since June 2008, though it later fell below that level.

(Editing by Jeffrey Benkoe)