* Yellen to speak at award presentation at 2:30 p.m. ET
* U.S. 10-year treasury yields hit two-week lows
* Valeant surges on better-than-expected profit
* Priceline, TripAdvisor fall on weak forecasts
* Indexes down: Dow 0.19 pct, S&P 0.17 pct, Nasdaq 0.45 pct (Updates to early afternoon)
By Tanya Agrawal
Nov 7 (Reuters) - Wall Street added to losses in early afternoon trading on Tuesday, with the S&P and the Dow weighed down by financial stocks and the Nasdaq slipping on weak forecast from travel services company, Priceline.
The financial sector led the decliners among the 11 major S&P sectors, with a 1.26 percent fall.
U.S. 10-year treasury yields hit a two-week low and briefly fell below the 200-day moving average.
Goldman Sachs weighed the most on the Dow, while JPMorgan and Bank of America were among the top three drags on the S&P.
Priceline fell 12.1 percent and that of travel-review website operator TripAdvisor hit a five-year low after the companies gave soft fourth-quarter profit forecasts.
Investors are also waiting for more clarity on President Donald Trump's tax-cut plan as the earnings season winds down.
Republicans plan to bring their tax overhaul bill for a vote next week, U.S. House Ways and Means Committee Chairman Kevin Brady said on Tuesday, adding that he expects the plan to pass.
House Republicans last week unveiled a first draft that proposed a range of cuts aimed at helping businesses, including slashing the corporate rate to 20 percent from 35 percent.
"The market is waiting for the next catalyst, which is the tax bill," said Adam Sarhan, chief executive of 50 Park Investments.
"It looks like, unless some major unforeseen event occurs, tax cuts will get passed in some shape or form. Whether (corporate tax cuts) it's 20 percent or 25 percent, a big tax cut is coming."
The S&P has risen about 15 percent in 2017 on the back on strong earnings, an improving economy and Trump's promise to cut taxes.
With more than 400 of S&P 500 companies having reported, earnings for the third quarter are expected to have climbed 8 percent, compared with expectations of a 5.9 percent rise at the start of October, according to Thomson Reuters I/B/E/S.
At 12:29 p.m. ET (1629 GMT), the Dow Jones Industrial Average was down 44.59 points, or 0.19 percent, at 23,503.83, the S&P 500 was down 4.56 points, or 0.17 percent, at 2,586.57.
The Nasdaq Composite was down 30.31 points, or 0.45 percent, at 6,756.12.
Defensive sectors such as utilities and consumer staples were the top gainers on the S&P.
Investors will also lend an ear to a speech from outgoing Federal Reserve Chair Janet Yellen at a presentation of the Paul H. Douglas Award for Ethics in Government in Washington at 2:30 p.m. ET.
Her speech will come less than a week after President Donald Trump chose Fed governor Jerome Powell to replace Yellen at the end of her term in 2018.
Valeant Pharma surged 15.2 percent after the company's profit beat Wall Street estimates.
Mallinckrodt sank to an all-time low after the drugmaker reported dismal quarterly revenue and warned of slower sales for Acthar, its biggest source of revenue.
Declining issues outnumbered advancers on the NYSE by 1,812 to 996. On the Nasdaq, 2,149 issues fell and 753 advanced. (Reporting by Tanya Agrawal; Editing by Arun Koyyur)