Indian equity benchmarks BSE Sensex and NSE Nifty50 are likely to make a gap-down opening on Tuesday, a day after both halted a three-day winning run, amid weakness across global markets as nervousness persisted among investors on steep hikes in interest rates and their impact on economic growth. Singapore Exchange (SGX) Nifty futures — an early indicator of the Nifty index — dropped as much as 130 points or 0.8 percent to 16,068.5.