US stocks fell on Tuesday in a modest retreat from the previous session's sharp rally, but major indexes remained on track for a positive first quarter and the S&P 500 was set for its ninth straight quarterly rise. Energy shares were in focus as crude oil fell 1.4 percent to $48 per barrel, sending the S&P Energy index down 0.6 percent as one of the weakest industry groups of the day. 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. The talks come when oversupply is already a major concern for energy investors, having contributed to crude falling more than 50 percent from a high in June. Endurance Specialty Holdings Ltd agreed to buy reinsurer Montpelier Re Holdings Ltd for about $1.83 billion, while Charter Communications Inc agreed to acquire Bright House Networks in a roughly $10 billion deal. Charter rose 7.9 percent to $197.89 while Montpelier rose 0.7 percent to $38.40. Endurance fell 4.3 percent to $61.55. Tuesday marks the end of the first quarter. Over the period, the Dow rose 0.5 percent, the S&P 500 rose 1.1 percent and the Nasdaq rose 4.1 percent. This is the ninth straight quarterly advance for the S&P and Nasdaq, the longest such streak for the S&P since 1998 and the longest for the Nasdaq in its history. Despite that, all three are set to be negative for March. The Dow Jones industrial average fell 63.76 points, or 0.35 percent, to 17,912.55, the S&P 500 lost 5.54 points, or 0.27 percent, to 2,080.7 and the Nasdaq Composite dropped 15.34 points, or 0.31 percent, to 4,932.11.