Stock index futures edged higher on Tuesday after earnings from blue chips like Ford extended optimism about a strong earnings season but the debt ceiling stalemate kept investors nervous.

Stocks fell in the previous session as lawmakers remained deadlocked over a deal to raise the government's debt ceiling to avoid default. Investors were hopeful a compromise could be crafted by the August 2 deadline.

President Barack Obama took to the airwaves last night to rally public support for a package proposed by Democrats, warned that failure to make a deal would severely hurt the nation.

Ford Motor Co shares were up 2.1 percent at $13.42 in premarket trade after the automaker's second-quarter earnings beat expectations, helped by higher prices and improved sales in North America.

Cummins Inc rose 5.5 percent to $112.49 after the diesel engine maker reported higher earnings.

But 3M Co fell 1.8 percent to $93.40 after the industrial conglomerate's quarterly earnings met estimates, but it said Japan's March earthquake and tsunami reduced sales and profit margins.

The basic theme of earnings season, which is positive, remains in the market, reflected by some of the results this morning like Ford, said Peter Cardillo, chief market economist at Avalon Partners in New York.

But the market will remain on edge due to the impasse. Investors are not expecting a default, but they are more worried about what kind of cuts will be made and what actions will be taken by politicians.

S&P 500 futures rose 2 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 were unchanged, and Nasdaq 100 futures added 3.75 points.

The May Standard & Poor's/Case-Shiller home price index will be released at 9 a.m. EDT. Economists in a Reuters survey expected the index to be unchanged versus a 0.1 percent drop in April.

At 10:00 a.m. EDT, the Conference Board reports on July consumer confidence. Economists expect a reading of 56.0, compared with 58.5 in June.

Also coming at 10 a.m., the Commerce Department releases new home sales for June. Economists forecast a total of 320,000 annualized units, compared with 319,000 in May.

Resource-related stocks will be in focus as copper prices rose for the first time in five sessions on a weaker dollar. Other key base metals also advanced.

U.S. specialty finance company Orchid Island Capital Inc postponed its initial public offering due to market conditions.

European shares <.FTEU3> were slightly down, while Japan's Nikkei average <.N225> closed up 0.5 percent.

(Reporting by Angela Moon; editing by Jeffrey Benkoe)