U.S. stocks were set to rise at the open on Tuesday on speculation Spain will soon request a bailout, seen by some as the necessary next step to alleviating the euro zone's debt crisis.

In a positive sign, Spain's borrowing costs moderated. Spanish 10-year bond yields fell below 5.76 percent after trading above 6 percent for at least part of the past four sessions. Spain's main stock index <.IBEX> gained 1.3 percent. <.EU>

"I think the market feels that we are closer to some type of action and resolution in terms of the Spanish problem," said Paul Mendelsohn, chief investment strategist at Windham Financial Services in Charlotte, Vermont. "That's certainly helping markets this morning."

But uncertainty could still turn markets volatile. In spite of Spain's apparent readiness to ask for help, Germany has signaled that it should hold off on its request, according to European officials on Monday.

Chrysler said September vehicle sales were up 12 percent from a year earlier and the highest for the month since 2007. Shares of majority stakeholder Fiat rose 2.6 percent in Milan.

JPMorgan Chase & Co was sued by New York's attorney general on Monday in the first action to come out of a working group created by President Barack Obama to go after wrongdoing that led to the financial crisis. The civil fraud lawsuit centered on mortgage-backed securities packaged and sold by Bear Stearns, which JP Morgan acquired.

JPMorgan shares edged up 0.3 percent in light premarket trading.

S&P 500 futures rose 6.4 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 rose 33 points, and Nasdaq 100 futures added 11 points.

PetSmart Inc shares added 2.9 percent before the opening bell after S&P Dow Jones Indices said after Monday's close the company will replace Sunoco Inc in the S&P 500 on October 4.

Shares of Express Inc fell 16 percent in premarket trading after the apparel retailer revised its third-quarter outlook.

Shares of ArQule Inc tumbled 62 percent after the biotechnology company and Japan's Daiichi Sankyo <4568.T> said they will end a late-stage trial of their experimental lung cancer drug.

Wall Street rose modestly on Monday, lifted by a surprising expansion in U.S. manufacturing in September.

(Reporting by Rodrigo Campos; Editing by Kenneth Barry)