* Indexes set for second weekly loss in a row
* Wall St seesaws after Yellen remarks
* Indexes up: Dow 0.5 pct, S&P 0.3 pct, Nasdaq 0.2 pct (Updates to late afternoon)
By Caroline Valetkevitch
Oct 14 (Reuters) - U.S. stocks held modest gains in volatile Friday afternoon trading as investors assessed comments by Federal Reserve Chair Janet Yellen on the U.S. economy.
Yellen, in a speech at a conference of policymakers and top academics, laid out the deepening concern at the Fed that U.S. economic potential is slipping - and may need aggressive steps to rebuild it.
Traders have currently priced in a 67-percent chance of a rate hike in December, while the odds for November are minimal as the Fed's meeting falls just days before the Nov. 8 U.S. presidential election.
"Is Chair Yellen now adding yet another reason for holding off raising rates in December? We'll have to watch the data as (we) move towards the mid-December FOMC meeting and more carefully monitor ... Yellen's guidance," said Quincy Krosby, market strategist at Prudential Financial.
Gains in bank shares helped to support the market, with the S&P 500 financial index up 0.8 percent, though shares of JPMorgan, Citigroup and Wells Fargo were mostly flat following their results.
The Dow Jones industrial average was up 95.79 points, or 0.53 percent, to 18,194.73, the S&P 500 gained 6.85 points, or 0.32 percent, to 2,139.4 and the Nasdaq Composite added 11.72 points, or 0.22 percent, to 5,225.05.
Shares of Twitter fell 5.9 percent after Salesforce.com's chief executive ruled out bidding for Twitter. Salesforce.com shares jumped 6.3 percent.
HP Inc fell 3.4 percent after the company said it would cut about 3,000 to 4,000 jobs over the next three years.
Advancing issues outnumbered declining ones on the NYSE by a 1.41-to-1 ratio; on Nasdaq, a 1.11-to-1 ratio favored advancers.
The S&P 500 posted 3 new 52-week highs and 3 new lows; the Nasdaq Composite recorded 23 new highs and 73 new lows. (Additional reporting by Yashaswini Swamynathan in Bengaluru; Editing by Nick Zieminski)