Mumbai, Feb. 20 -- The military build-up in the Persian Gulf and a muddied US interest rate outlook dealt the biggest blow to Indian markets since the Union budget, with investors losing nearly Rs.6.8 trillion on Thursday. The benchmark Nifty plunged 1.4% to close at 25,454.35 while the Sensex shed 1.5% to 82,498.14. The broader market wasn't spared either-the Nifty Midcap 100 slumped 1.6%, while the Nifty Smallcap 250 fell 1.2%. Among Nifty's biggest laggards were IndiGo (-3.3%), UltraTech Cement (-2.9%), and Mahindra & Mahindra (-2.9%). The Wall Street Journal reported that the US has gathered the biggest air power in West Asia since the 2003 invasion of Iraq. A strike on Iran could trigger a spike in oil prices, as markets react to the prospect of Iran blockading the Strait of Hormuz, a critical chokepoint for 21% of the world's oil supply. Meanwhile, the US Federal Reserve made a near-unanimous decision to keep interest rates unchanged, minutes of the latest meeting showed, with policymakers striking a cautiously hawkish tone. "The sugar high from tax cuts will fade eventually, and the jobs situation remains challenging; without meaningful job creation, a sustained revival in consumption might be hard to achieve," said Saurabh Mukherjea, founder and chief investment officer of Marcellus Investment Managers. While the India-US trade deal has lifted sentiment at the margins, the deal's fine print will ultimately determine whether investor confidence gets a durable boost, he added. At the same time, markets will be closely tracking commentary from Kevin Warsh, the new Fed chair, for cues on the trajectory of interest rates, Mukherjea said....