US STOCKS-S&P, Nasdaq slip as Citi, Apple weigh

* Citi falls as results miss expectation

* Apple off after CEO Jobs takes leave, to post results

* Indexes: Dow up 0.2 pct, S&P, Nasdaq flat

* For up-to-the-minute market news see [STXNEWS/US] (Updates to open)

By Angela Moon

NEW YORK, Jan 18 (Reuters) - The S&P and Nasdaq dipped on Tuesday after Citigroup's quarterly results missed estimates and Apple's Chief Executive Steve Jobs took another medical leave.

Citigroup Inc <C.N> fell 4.5 percent to $4.91 after the No. 3 U.S. bank posted a $1.3 billion quarterly profit but missed estimates as revenue slumped. For details, see [ID:nN18118584]

Apple Inc <AAPL.O> dropped 4.1 percent to $334.01 after the company said Jobs is taking his third medical leave since 2004, reviving concerns about the future of the maker of the iPad and iPhone. Apple is due to report quarterly results later Tuesday. For details, see [ID:nSGE70G0AY] and [ID:nL3E7CI0LO]

"The market's reaction to Steve Jobs' surprise medical leave from Apple today will underscore the importance of the tech sector on the S&P 500 ... What happens next to Apple will therefore dominate what happens in the sector and the S&P as well," said Bryan McCormick, analyst at optionMonster.com.

The Dow Jones industrial average <.DJI> added 28.23 points, or 0.24 percent, at 11,815.61. The Standard & Poor's 500 Index <.SPX> was down 0.16 point, or 0.01 percent, at 1,293.08. The Nasdaq Composite Index <.IXIC> was up 1.06 points, or 0.04 percent, at 2,756.36. (Reporting by Angela Moon; editing by Jeffrey Benkoe)