* AutoZone up early, results show profit growth
* Carnival slides, hurt by downgrades, forecast of loss
* Futures: Dow up 3 pts, S&P down 2.5 pts, Nasdaq down 2 pts
NEW YORK, Sept 25 (Reuters) - U.S. stock index futures were little changed on Wednesday, following four days of losses on the S&P 500 and Dow, as investors grew increasingly concerned about budget and debt negotiations in Washington.
Concerns over a potential U.S. government shutdown, and mixed signals on the immediate future of the monetary policy that has given support to equities, kept investors on edge. The possibility of a last-minute deal in Congress, however, eased the selling pressure brought by the uncertainty.
"Investors are not willing to sell the market only to see some kind of agreement reached that would give it support, nor jump in knowing it could get a lot uglier before it is resolved," said Rick Meckler, president of investment firm LibertyView Capital Management in Jersey City, New Jersey.
He said there was confidence an agreement would eventually be reached, but "it seems we can't get out of the way of the political games that surround funding and operating the government."
S&P 500 futures fell 2.5 points and were slightly lower in terms of 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 rose 3 points, and Nasdaq 100 futures lost 2 points.
The Commerce Department releases August durable goods orders at 8:30 a.m. EDT (1230 GMT). Economists in a Reuters survey expect an unchanged reading for August orders after a 7.4 percent drop in July. New home sales data for August is due at 10:00 a.m. (1400 GMT).
AutoZone shares dipped 0.5 percent in light premarket trading after the largest U.S. auto parts retailer reported a 15 percent rise in quarterly profit, mainly due to higher margins.
Carnival Corp shares fell 4.3 percent in premarket trading after several brokerage downgrades in the wake of the company's warning it could report an adjusted loss for the current quarter.
In budget negotiations in Washington, most Republicans shunned Senator Ted Cruz's diatribe overnight against President Barack Obama's health insurance reform law, which is delaying Senate consideration of a stop-gap funding measure needed to avoid a government shutdown in six days. Last week, the Republican-controlled House of Representatives passed a version of the spending measure that denied funds to "Obamacare," but that will be stripped from the Senate version.
The House will have to decide whether to pass the revised bill or find a compromise with the Senate. Unless new funding is quickly approved, a government shutdown would begin on Tuesday.