Stocks were set to edge higher at the open on Tuesday as investors hoped S&P's downgrade warning for the euro zone would help force budget changes at a European Union summit this week.

The pan-European FTSEurofirst 300 index edged 0.4 percent lower a day after rating agency Standard & Poor's said it may cut the sovereign credit rating of 15 euro zone countries.

S&P's warning may help France and Germany force changes to EU rules, restore market confidence and prevent a sovereign debt crisis from widening.

There's an idea the S&P warning is likely to push the EU to work harder at solving its debt crisis, said Rick Meckler, president of investment firm LibertyView Capital Management in New York.

It may have the impact of pushing forward the solution without having to be an actual problem to the market.

S&P 500 futures rose 0.2 point and were flat in terms of 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 14 points, and Nasdaq 100 futures added 8.75 points.

The S&P threat could help French President Nicolas Sarkozy and German Chancellor Angela Merkel pass a change to the EU treaty that could allow penalties on countries that exceed deficit targets.

Traders were also encouraged by a dip in Italian benchmark bond yields, which had soared close to 8 percent recently, threatening government financing and bringing the third largest euro zone economy closer to a sovereign default.

Every time yields come down, it gives (Italy) a little more room to survive until reforms are put in place, Meckler said. Italy's new government has passed an austerity package in hopes of easing its fiscal crisis.

The yield on Italian 10-year notes dipped below 6 percent, the lowest since late October.

The S&P warning was leaked during U.S. market hours on Monday, deeply cutting into stock gains.

In company news, Darden Restaurants Inc cut its fiscal 2012 earnings and sales forecast as deep discounts at its Olive Garden chain failed to bring new business. Darden fell 7.1 percent to $44.32 in premarket trading.

(Reporting by Rodrigo Campos; editing by Jeffrey Benkoe)

Germany