The Sensex at the Bombay Stock Exchange dropped 65 points, or 0.3 percent, to 19,700 in afternoon trade, a short while ago, on profit-booking by investors, amid weak regional markets. Earlier in the morning, the Sensex had lost 43 points, to 19,721. The Sensex had gained over 340 points in the past three trading sessions.Stock markets in China, Hong Kong, Singapore, Taiwan and South Koreawere down by between 0.1 percent and 0.8 percent, today, on concerns over the US central bank's quantitative easing. Wall Street's Dow Jones Industrial Average had lost 0.2 percent, overnight.The rupee today weakened by 33 paise to 54 rupees 83 paise against the dollar in early trade due to increased demand for the US currency from importers amid firm global cues. The rupee had lost 15 paise to close at 54 rupees 50 paise against the US dollar yesterday.