* Energy, utility shares weigh
* Union Pacific up on profit beat
* Indexes down: Dow 0.5 pct, S&P 0.4 pct, Nasdaq 0.3 pct (Updates to late afternoon)
By Caroline Valetkevitch
NEW YORK, Jan 19 (Reuters) - U.S. stocks added to losses in afternoon trading on Thursday, led by declines in utilities and energy shares, with investors cautious ahead of Donald Trump's inauguration on Friday.
The Dow was on track to mark a fifth day of declines, moving further away from 20,000. The S&P 500 utilities index, down 0.9 percent, led losses, followed by energy, down 0.7 percent.
The post-election rally in stocks has slowed in recent weeks as investors look for more details on Trump's policies.
Traders in the options market have grown increasingly cautious and have been loading up on defensive contracts, even as overall levels of stock market volatility are close to record lows.
"People are little bit jittery ahead of the inauguration and after the rally we've had," said Peter Tuz, president of Chase Investment Counsel in Charlottesville, Virginia. "I'm not surprised the market is down."
At 2:53 p.m. ET, the Dow Jones Industrial Average was down 89.48 points, or 0.45 percent, to 19,715.24, the S&P 500 lost 9 points, or 0.4 percent, to 2,262.89 and the Nasdaq Composite dropped 15.98 points, or 0.29 percent, to 5,539.68
Yellen said on Wednesday the U.S. economy was getting closer to running on its own, adding that it made sense to raise interest rates gradually. She will speak on monetary policy at Stanford University later in the day.
Adding to recent robust economic data, U.S. homebuilding rebounded more than expected in December and weekly jobless claims fell to a 43-year low.
Among gainers, railroad CSX Corp jumped 18.3 percent after a source said CP Rail CEO Hunter Harrison, who steps down on Jan. 31, is in advanced talks to team up with a former Pershing Square Capital partner to shake up CSX.
Union Pacific was up 2.2 percent at $106.07 after better-than-expected quarterly net profit.
Declining issues outnumbered advancing ones on the NYSE by a 3.66-to-1 ratio; on Nasdaq, a 2.61-to-1 ratio favored decliners.
The S&P 500 posted 15 new 52-week highs and 2 new lows; the Nasdaq Composite recorded 65 new highs and 33 new lows. (Additional reporting by Yashaswini Swamynathan in Bengaluru; Editing by Anil D'Silva and Nick Zieminski)