U.S. stock index futures were higher on Tuesday as investors awaited testimony from U.S. Federal Reserve Chairman Ben Bernanke, who is not expected to cut short the Fed's bond buying program.

Much of the market's nearly uninterrupted gains over the past several months have come since the Fed announced its $600 billion stimulus program. Investors have been concerned about the impact of ending it early.

Bernanke, slated to speak to the U.S. Senate Banking Committee, is expected to remain cautious about the economy despite recent data pointing to improvement.

The dollar <.DXY> stayed near a three-and-a-half month low against a currency basket on the view that the Fed will stick with its loose monetary policy.

Overseas, forces loyal to Libyan leader Muammar Gaddafi were massed in the western part of the country, residents said, while the United States said it was moving warships and air forces closer to the North African nation.

Market participants have been watching the Libyan situation to see its impact on energy prices. April crude futures were up 0.1 percent to $97.11 per barrel, still at levels elevated since the unrest began.

S&P 500 futures rose 5.9 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 added 71 points and Nasdaq 100 futures rose 14.25 points.

February ISM manufacturing data will be released at 10 a.m. EST, along with January construction spending data. The ISM number is seen rising to 61 from 60.8 in the previous month, while construction spending is expected to show a narrower rate of decline than in the previous month.

Fresh Del Monte Produce Inc reported adjusted fourth-quarter earnings and revenue that missed expectations, while AutoZone Inc and CenterPoint Energy Inc are set to report quarterly results.

General Mills Inc and Nestle SA are among leading candidates to buy a 50 percent stake in French yogurt maker Yoplait, Bloomberg reported, citing sources.

Stocks rose for a second straight session Monday after billionaire investor Warren Buffett, chairman of Berkshire Hathaway Inc , said the conglomerate needed to make major acquisitions, a sign stocks may be cheap.

(Editing by Jeffrey Benkoe)

Libya Warren buffett Ben Bernanke