* UnitedHealth jumps after 4th-quarter results
* GE slides after saying it would take $6.2 bln 4th-quarter charge
* Merck gains on positive Keytruda lung cancer data
* Dow flat, S&P down 0.2 pct, Nasdaq down 0.3 pct (Updates to late afternoon, changes byline, adds NEW YORK dateline)
By April Joyner
NEW YORK, Jan 16 (Reuters) - Wall Street's major stock indexes pared gains in late afternoon trading on Tuesday as lower oil prices weighed on the energy sector.
The energy sector fell 1.0 percent as Brent crude oil shed some of its recent gains, falling nearly $1 per barrel. Industrials and materials were the other major laggards on the S&P, down 0.9 percent and 1.3 percent, respectively.
The CBOE Volatility index, a widely followed measure of market anxiety, rose to a more than 1-month high of 11.51.
"Lower energy prices are taking us down a little bit," said Tracie McMillion, head of global asset allocation strategy at Wells Fargo Investment Institute in Winston-Salem, North Carolina.
But, she added, "investors are continuing to move into equities as they see returns. It's feeding on itself, becoming a virtuous cycle, enticing more people in."
Indeed, earlier on Tuesday, the Dow Jones Industrial Average had broken past the 26,000 mark for the first time as fourth-quarter earnings season got off to a strong start following upbeat results from UnitedHealth and Citigroup.
UnitedHealth rose 2.3 percent after the largest U.S. health insurer reported results that beat estimates and raised its 2018 earnings outlook.
More than three quarters of the 30 S&P 500 companies that have reported so far have topped profit estimates, according to Thomson Reuters I/B/E/S.
The Dow Jones Industrial Average rose 10.61 points, or 0.04 percent, to 25,813.8, the S&P 500 lost 5.45 points, or 0.20 percent, to 2,780.79 and the Nasdaq Composite dropped 21.21 points, or 0.29 percent, to 7,239.85.
Merck surged 6.4 percent after early results from a key study showed its blockbuster drug Keytruda and two chemotherapy medicines helped lung cancer patients live longer and stopped the disease from advancing.
General Electric fell 3.4 percent after raising the prospect of breaking itself up and announced more than $11 billion in charges from its long-term care insurance portfolio and new U.S. tax laws.
Viacom fell 6.1 percent after sources told Reuters CBS Corp and the company were not in active merger discussions.
Declining issues outnumbered advancing ones on the NYSE by a 2.00-to-1 ratio; on Nasdaq, a 2.37-to-1 ratio favored decliners.
The S&P 500 posted 170 new 52-week highs and five new lows; the Nasdaq Composite recorded 240 new highs and 26 new lows. (Additional reporting by Sruthi Shankar in Bengaluru; Editing by Anil D'Silva and James Dalgleish)