US STOCKS-Wall St retreats but indexes set for quarterly gain
* Oil prices weaken for third straight day
* Charter to buy Bright House for about $10 bln
* Nasdaq set for longest-ever streak of quarterly gains
* Dow down 0.6 pct, S&P 500 down 0.4 pct, Nasdaq down 0.5 pct (Updates to midday)
By Caroline Valetkevitch
NEW YORK, March 31 (Reuters) - U.S. stocks declined on Tuesday in a retreat from the previous session's sharp rally, but major indexes remained on track for first-quarter gains and the S&P 500 was set for its ninth straight quarterly rise.
Energy shares were in focus as crude oil fell, sending the S&P Energy index down 0.5 percent. Exxon Mobil Corp fell 0.7 percent to $85.06.
Oil was pressured as Iran and six world powers entered a final day of talks on a nuclear deal that could see the energy-rich country increase oil exports. Oversupply is already a major concern for energy investors, with crude falling more than 50 percent from a June high.
The day's decline in stocks follows gains of more than 1 percent on each of the major indexes on Monday. Continuación...