US STOCKS-Dow breaches 26,000 mark on robust earnings reports

* Citigroup, UnitedHealth jump after Q4 results

* GE slides after saying it would take $6.2 bln charge

* Indexes up: Dow 0.87 pct, S&P 0.65 pct, Nasdaq 0.85 pct (Updates to open)

Jan 16 (Reuters) - Wall Street's main indexes rose sharply on Tuesday, with the Dow hitting the 26,000 mark for the first time, as the fourth-quarter earnings season kicked into high gear.

UnitedHealth rose 2.2 percent after the largest U.S. health insurer reported results that beat analysts' estimates and raised its full-year profit forecast.

Citigroup Inc jumped 1.4 percent after the lender reported profit that topped Wall Street expectations as strength in consumer businesses made up for lower revenue from bond and currency trading.

Hopes of strong quarterly earnings, supported by steep cut in corporate taxes, and solid global economic growth have bolstered Wall Street's optimism in the start to 2018.

"Not only is the U.S. coming off a strong quarter, but the new tax reform measures are continuing to provide a boost, with investors keen to hear more about what impact this will have on future earnings," said Craig Erlam, senior market analyst at online foreign exchange broker Oanda.

More than three quarters of the 26 S&P 500 companies that have reported so far have topped profit estimates, according to Thomson Reuters I/B/E/S.

At 9:41 a.m. ET (1441 GMT), the Dow Jones Industrial Average was up 225.34 points, or 0.87 percent, at 26,028.53, helping it record its fastest 1000-point rise. It ended above 25,000 on Jan. 4.

The S&P 500 was up 18.09 points, or 0.65 percent, at 2,804.33 and the Nasdaq Composite was up 62.08 points, or 0.85 percent, at 7,323.14.

General Motors rose 2.7 percent after the company said it expected earnings in 2018 to be largely flat, compared with 2017, but that profits should pick up pace in 2019.

General Electric shares fell 3.7 percent after the industrial conglomerate said it would record a $6.2 billion charge in the fourth quarter as part of an ongoing review of its finance arm's insurance portfolio.

The S&P energy index fell 0.3 percent as oil prices pulled back from recent highs, with Brent crude dipping 1.07 percent to $69.51 per barrel.

Nine of the 11 major S&P sectors were higher, led by a 1.44 percent rise in the real estate index and 0.92 percent gains in the technology index SPLRCT>.

Amazon rose more than 2 percent, extending gains from last week when data showed U.S. holiday spending surged to 12-year high, prompting price target hikes.

Bitcoin tumbled 18 percent to a four-week trough close to $11,000, after reports that a ban on trading of cryptocurrencies in South Korea was still an option.

Shares of cryptocurrency-related companies were all down. Marathon Patent, Riot BlockChain, Xunlei and Overstock.com fell between 7.7 percent and 11 percent.

Advancing issues outnumbered decliners on the NYSE by 2,037 to 687. On the Nasdaq, 1,958 issues rose and 673 fell. (Reporting by Sruthi Shankar in Bengaluru; Editing by Anil D'Silva)