* For the week, S&P, Nasdaq on track to rise, Dow set for decline
* Boeing biggest drag on Dow; Apple weighs on S&P, Nasdaq
* Disney falls after rating cut
* Indexes down: Dow 1.4 pct, S&P 1 pct, Nasdaq 0.92 pct (Updates to late afternoon, changes byline)
By Marcus E. Howard
Dec 18 (Reuters) - U.S. stocks fell on Friday afternoon for the second day in a row, as crude oil prices headed for their third weekly loss and stock and index options contracts were set to expire.
All S&P sectors were down, led by financial stocks, which were down 1.8 percent.
The biggest drag on the financial index, Berkshire Hathaway , was down 2.4 percent, while Wells Fargo, and Citigroup were down more than 2 percent and JPMorgan was off 1.9 percent.
Wall Street remained anxious over an oil glut amid a demand slowdown. U.S. crude futures fell to their lowest level in nearly seven years at $34.29 a barrel. Brent crude was headed for its third week of losses, down almost 1 percent at $36.72.
Still, the energy sector, down 0.4 percent in afternoon trading, was one of the better-performing sectors of the day, said David Lefkowitz, senior equity strategist at UBS Wealth Management Americas in New York.
"It's a little bit hard to explain just based upon the news flow," said Lefkowitz. "I don't know if this is just a little bit volatility after the Fed - it's certainly possible."
The week has been dominated by the Federal Reserve, which raised rates on Wednesday for the first time in nearly a decade.
A new Reuters poll of economists found two-thirds expect the Fed to raise interest rates again in the next three months, though not as quickly as some policymakers have suggested.
Volatility was slightly higher than usual on account of "quadruple witching" - the expiry of options on stocks and indexes as well as futures on indexes and single stocks.
While higher volume and a pick-up in volatility are not unusual on options expiration day, Randy Frederick, managing director of trading and derivatives for Charles Schwab in Austin, Texas, said Friday's sell-off appeared to be tied more to the Fed's move and lower oil prices.
"I think the market is more sensitive to oil than anything else. If we see oil continue to hit record lows by the end of the day, I think the market will follow it," he said.
At 2:34PM the Dow Jones industrial average fell 239.81 points, or 1.37 percent, to 17,256.03, the S&P 500 lost 20.41 points, or 1 percent, to 2,021.48 and the Nasdaq Composite dropped 46.17 points, or 0.92 percent, to 4,956.38.
The S&P and Nasdaq were set for a 0.4 percent increase for the week while the Dow was headed for a 0.2 percent decline.
Boeing's 4.2 percent fall weighed the most on the Dow, while Apple weighed on the S&P and Nasdaq with a 1.8 percent decline.
Disney was down 3.2 percent at $108.79, after BTIG downgraded the stock to sell.
Declining issues outnumbered advancing ones on the NYSE by 1,888 to 1,171, for a 1.61-to-1 ratio on the downside; on the Nasdaq, 1,695 issues fell and 1,115 advanced for a 1.52-to-1 ratio favoring decliners.
The S&P 500 posted 1 new 52-week highs and 31 new lows; the Nasdaq recorded 21 new highs and 105 new lows.
Reporting by Marcus E. Howard, additional reporting by Saqib Ahmed in New York, Abhiram Nandakumar and Aastha Agnihotri in Bengaluru; Editing by Don Sebastian and Dan Grebler