Stocks were set to open slightly higher on Monday, helped by optimism about shares' performance in the third quarter, while a profit warning from Citigroup Inc was expected to weigh on the financial sector.

In another bank-related development, Switzerland's UBS AG announced that it plans a $3.4 billion write-down.

On the economic agenda, data on U.S. manufacturing in September was due at 10 a.m. EDT.

Monday marks the start of the fourth quarter, and some investors expect more gains, said Rick Meckler, president of investment firm LibertyView Capital Management in Jersey City, New Jersey. For the third quarter, the Dow was up 3.6 percent, the S&P was up 1.6 percent and the Nasdaq was up 3.8 percent.

Adding to the positive tone, cell phone maker Nokia said it will offer $8.1 billion for U.S.-based digital map supplier Navteq.

S&P 500 futures edged up 1.60 points, above fair value, a mathematical formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract.

Dow Jones industrial average futures were up 6 point, and Nasdaq 100 futures were unchanged.

In other earnings news, Walgreen Co, one of the largest drug store chains, posted an unexpected decline in quarterly profit. The stock fell 9.2 percent to $42.91 before the bell.

Shares of Citigroup, the largest U.S. bank by market value and a Dow component, declined 2.3 percent to $45.60 in trading before the opening bell. Citigroup said it expects to report a 60 percent drop in third-quarter profit.

I think people are expecting there were some losers in the whole subprime (sector) and that not all of the bad news had come out yet, Meckler said. Now, for some of the banks, it's probably worse than people thought it would be.

The negative impact on the market could be limited if investors see it as a sign the Federal Reserve will need to continue cutting interest rates, Meckler said.

The Institute for Supply Management's manufacturing index for September is expected to show a reading of 52.6, down from 52.9 in August, according to a Reuters poll of economists.

UBS AG, the world's largest wealth manager, also swept out senior managers and slashed jobs in one of the biggest casualties yet from the worldwide credit crunch.

Other bank shares trading lower before the bell were JPMorgan Chase & Co., down 0.9 percent at $45.39, and Bank of America, down 0.7 percent at $49.90.