Indian equity benchmarks BSE Sensex and NSE Nifty50 are likely to open sharply lower on Wednesday, following two back-to-back days of gains, amid nervousness across global markets ahead of a key rate decision by the Fed. Singapore Exchange (SGX) Nifty futures — an early indicator of the Nifty index — fell as much as 94.5 points or 0.5 percent to 17,700.5 ahead of the opening bell on Dalal Street.