* Abu Dhabi gives Dubai $10 bln in bailout money
* XTO Energy jumps on Exxon buyout
* Citigroup to repay TARP money through stock issue
* Dow up 0.3 pct; S&P up 0.6 pct: Nasdaq up 0.9 pct
* For up-to-the-minute market news, click [
] (Updates to afternoon, changes byline)By Chuck Mikolajczak
NEW YORK, Dec 14 (Reuters) - U.S. stocks rose on Monday as Abu Dhabi's $10 billion in aid to help Dubai avoid default eased concerns, and a takeover deal by Exxon Mobil Corp raised optimism about mergers and acquisitions.
Citigroup Inc's plan to repay the U.S. government about $20 billion in bailout funds also helped buttress optimism.
Exxon Mobil <XOM.N> said it would buy natural gas supplier XTO Energy Inc <XTO.N> in an all-stock transaction valued at about $30 billion, excluding debt. For details see [
].Abu Dhabi said on Monday it will provide Dubai $10 billion in bailout money, with $4.1 billion for payment on a maturing bond. [
]."It's helping -- everyone kind of scratched their head, so we can't rely on a country or city-state to step up?'" said Edward Hemmelgarn, chief investment officer of Shaker Investments in Cleveland.
"People have just gone back to it, helped calm fears a little bit and then people think about something else."
The Dow Jones industrial average <
> gained 33.03 points, or 0.32 percent, to 10,504.53. The Standard & Poor's 500 Index <.SPX> rose 7.13 points, or 0.64 percent, to 1,113.54. The Nasdaq Composite Index < > climbed 19.03 points, or 0.87 percent, to 2,209.34.Citigroup <C.N> laid out a plan to repay the money it owes the U.S. government, including raising money by selling $17 billion of common stock immediately, as the bank looks to end the restrictions on executive pay that came with the funds. [
].Citi's stock slumped 6.6 percent to $3.69.
Shares of XTO climbed 15 percent to $47.72, while Exxon Mobil shed 4.4 percent to $69.64. The NYSE Arca Natural Gas index <.XNG> gained 4.6 percent.
The First Trust ISE-Revere Natural Gas Index Fund <FCG.P>, an exchange-traded fund of natural gas companies' shares, rose 5.1 percent. XTO has underperformed that ETF by roughly 14 percent this year.
Sun Microsystems Inc <JAVA.O> shares advanced 10.5 percent to $9.23 on Nasdaq after European Union regulators signaled they could clear Oracle Corp's <ORCL.O> $7 billion takeover of Sun after Oracle promised measures to ease competition concerns. [
]. Oracle's stock rose 1.9 percent to $23.22.Visa Inc <V.N> shares rose 3.3 percent to $84 after ratings agency Standard & Poor's said late Friday the credit card company will replace telecommunications equipment maker Ciena Corp <CIEN.O> in the S&P 500 after the close of trading on December 18.
S&P also said Bristol-Myers Squibb split-off Mead Johnson Nutrition Co <MJN.N> will relace bond insurer MBIA Inc <MBI.N> on the same date. [
]. Mead Johnson shares rose 1.9 percent to $43.26.(Editing by Kenneth Barry)