U.S. stocks could open on a tentative note on Wednesday amid simmering geopolitical tensions. Futures of all three major indices were marginally up as investors weighed escalating tensions between Russia and Ukraine, and earnings from AI bellwether Nvidia Corp. NVDA.U.S. equity markets have had a mixed week so far, with the Dow Jones facing pressure even as the S&P 500 and Nasdaq witnessed sideway movements.FuturesChange (+/-)Nasdaq 1000.11%S&P 5000.12%Dow Jones0.19%R2K-0.09%In premarket trading on Wednesda ...