Indian equity benchmarks BSE Sensex and NSE Nifty50 are likely to make a gap-down opening on Monday tracking weakness across global markets amid concerns about aggressive rate hikes following hawkish commentary from the Fed. At 8:56 am, Singapore Exchange (SGX) Nifty futures -- an early indicator of the Nifty50 index -- were down 222 points or 1.3 percent at 16,958.