Stock index futures pointed to a slightly higher open on Wednesday as investors remained cautiously optimistic about progress on plans to lessen the euro zone's debt woes.

International auditors headed to Greece to scrutinize new austerity measures they must endorse for Athens to get the next tranche of aid.

German Chancellor Angela Merkel suggested that parts of a planned new 109-billion-euro ($148.6 billion) rescue for the debt-laden country could be reopened, depending on the outcome of the audit.

Recent efforts to solidify a euro zone rescue fund and alleviate the region's sovereign debt crisis lifted stocks on Tuesday for a third consecutive session and came after four straight days of losses for the benchmark S&P 500.

At least they are doing something and for the moment it has taken away the fear of a collapse for now, said Frank Lesh, a futures analyst and broker at FuturePath Trading LLC in Chicago.

It is certainly interesting that we had that nice rally yesterday and gave it all back late afternoon but it just shows how nervous the markets are and it is tough to commit. We will probably continue like this until there is a little more clarity and who knows when that comes.

Market volatility could remain as traders react to European headlines.

Analysts also said equities would be supported by quarter-end window dressing, when portfolio managers drop underperforming stocks and buy outperformers.

S&P 500 futures rose 3.7 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures gained 35 points, and Nasdaq 100 futures added 4.5 points.

In the latest economic data, new orders for long-lasting U.S. manufactured goods slipped in August on weak demand for motor vehicles, but a rebound in a gauge of business spending suggested the economy would avoid another recession.

In the latest quarterly earnings reports, spicemaker McCormick & Co Inc posted a profit that topped estimates, while discount chain Family Dollar Stores Inc recorded higher quarterly income.

Darden Restaurants Inc, parent of the Red Lobster and Olive Garden chains, posted a 6 percent drop in earnings.

Family Dollar shares slid 8 percent to $53.75 and Darden ticked up 2 cents to $47 in premarket trade.

(Reporting by Chuck Mikolajczak; editing by Jeffrey Benkoe)