Before the bell:

U.S. stocks will be weighed down by tech and bank shares at Tuesday's open following weak earnings from Citigroup, and worries about Apple CEO Steve Jobs' leave of absence.

Nasdaq-100 (COMP) futures, a proxy for the tech sector, slumped ahead of the opening bell. S&P 500 (SPX) futures were flat, and Dow Jones industrial average (INDU) moved slightly higher.
Last week ended with the Dow and the S&P posting their seventh straight week of gains. That's the longest streak for the Dow since the two months of consecutive gains that ended last April.
Companies: Investors will be keeping a close eye on Apple's stock Tuesday. Shares of the tech giant closed down 6.1% in Frankfurt, after Monday's announcement from Jobs. In U.S. pre-market trading Tuesday, shares of Apple dipped about 5%.
Apple (AAPL, Fortune 500) will release quarterly results after the bell, and the maker of computers and personal electronics is expected to post a profit of $5.39 a share on $24.4 billion in revenue. Analysts and investors are also eagerly awaiting details on how many iPads Apple sold during the tablet's first holiday season.
Citigroup (C) posted earnings before the opening bell that missed expectations, while revenue fell in line with forecasts. The bank reported a profit of $1.3 billion, or 4 cents per share, on revenue of $18.4 billion.
Analysts surveyed by Thomson Reuters had expected Citigroup to post earnings per share of 8 cents on $20.4 billion in revenue. Shares of Citi slipped 3% in pre-market trading.
Rival JPMorgan Chase (JPM) laid the foundation for strong bank earnings on Friday when it reported a 47% jump in fourth-quarter earnings to $4.8 billion, or $1.12 per share.
Delta (DAL) also reported quarterly earnings that missed forecasts, posting earnings of 19 cents per share -- compared to the 24 cents expected by analysts. Shares of the airline company dropped 3.5% before the opening bell.
IBM (IBM) is slated to report quarterly results after the closing bell Tuesday, with analysts predicting the company earned $4.08 per share.
Economy: The New York Fed released its Empire Manufacturing Survey before the market open. The reading ticked up to 11.92 in January, which was in line with expectations.
World markets:

Oil for February delivery edged down 29 cents to $91.25 a barrel.
Gold futures for February delivery added $14 to $1,374.50 an ounce.
The price on the benchmark 10-year U.S. Treasury rose, pushing the yield down to 3.29% from 3.33% late Friday.