US STOCKS-Citi boosts Wall St; IBM, Apple slide after close

* Citigroup beats on earnings, lifting sector

* Apple, IBM slide after the close as index futures drop

* Indexes: Dow up 0.7 pct; S&P up 0.7 pct; Nasdaq up 0.5

* For up-to-the-minute market news see [STXNEWS/US] (Adds share action after Apple, IBM report earnings; updates with trading volume)

By Edward Krudy

NEW YORK, Oct 18 (Reuters) - U.S. stocks advanced on Monday as stronger-than-expected profit from Citigroup helped financial shares shake off worries that the foreclosure mess could threaten the stability of the housing market.

Apple Inc , which hit an all-time high during the regular session, disappointed investors after reporting gross margins and iPad shipments. Its shares skidded 5 percent in after-hours trading while stock index futures fell, suggesting a weak market opening on Tuesday. For details, see [ID:nN18288374].

Shares in IBM also fell after the closing bell, losing 3.5 percent to $137.84. The stock had reached a 52-week high during the regular session. International Business Machines Corp reported a higher-than-expected profit and raised its outlook for the full year, but the shares fell on sluggish sales of technology services. [ID:nN18152165].

"Both stocks have kind of gone parabolic into the earnings," said Nick Kalivas, an analyst at MF Global in Chicago. "My fear is we're going to get a buy the rumor, sell the fact trade."

In regular trading, Citigroup gained 5.6 percent to $4.17 after it reported its third consecutive quarterly profit. Last week JPMorgan Chase and Co's profits beat estimates. The KBW Bank index <.BKX> rose 3 percent, recovering some of the losses banks had in the last few days.

The Dow Jones industrial average <.DJI> rose 80.91 points, or 0.73 percent, at 11,143.69. The Standard & Poor's 500 Index <.SPX> gained 8.52 points, or 0.72 percent, at 1,184.71. The Nasdaq Composite Index <.IXIC> added 11.89 points, or 0.48 percent, at 2,480.66.

Citigroup said it is looking at the home loans it bundled into bonds and sold to investors. So far, it has not found any problems.

The largest U.S. bank, Bank of America , reports earnings on Tuesday. Bank of America's shares rose 3 percent to $12.40.

Before the close on Monday, around 10 percent of S&P 500 companies had reported earnings, with 84 percent of those beating expectations, according to data compiled by Thomson Reuters.

Apple shares hit a life high at $319 during the day as analysts expected fourth-quarter earnings to showcase Apple's powerful one-two punch of the iPhone and the iPad.

Apple's shares closed up 0.4 percent to $315.79, then fell in extended-hours trading to $301.79. Traders in Apple's options were pricing in a potential post-earnings swing of about 7.5 percent.

Shares of IBM rose 1.3 percent to $142.83 and were the top boost to the Dow industrials before the company's earnings report.

Northeast Utilities will buy NSTAR in a $4.2 billion all-stock deal to create one of the largest U.S. utilities, the companies said. Shares in both companies fell, with Northeast down 0.9 percent to $30.42 and NSTAR off 0.6 percent to $39.30.

Advancing stocks outnumbered declining ones on the NYSE by a ratio of about 2 to 1. The ratio was about the same on the Nasdaq.

About 7.66 billion shares traded on the New York Stock Exchange, the American Stock Exchange and the Nasdaq -- below the year's average so far of about 8.77 billion. (Reporting by Edward Krudy; Additional reporting by Doris Frankel; Editing by Kenneth Barry)