Mumbai, Oct. 17 -- The Indian rupee extended gains in opening trades on Friday tracking weakness in dollar overseas. Benchmark indexes Sensex and Nifty jumped over 1 percent each on Thursday after reports suggested that talks on a bilateral trade agreement between India and the United States have picked up pace. INR opened at Rs 87.91 per dollar and hit a high of 87.75 so far during the day, near a one and half month high. Yesterday, rupee surged 21 paise to close at 87.87 against the US dollar on Thursday, buoyed by a softer American currency against major currencies and renewed risk-on sentiment among investors. At the interbank foreign exchange, the rupee opened below the 88-mark at 87.76 against the greenback, and touched an intraday ...