Futures make tentative gains ahead of Powell testimony

U.S. stock index futures notched cautious gains on Wednesday, ahead of Federal Reserve Chair Jerome Powell's testimony for clues on interest rates as the Ukraine crisis exacerbates concerns about inflation and growth. The mood remained dour across global stock markets as Brent crude jumped to near eight-year highs and metal prices rallied after Western sanctions disrupted transport of commodities exported by Russia. Wall Street indexes closed sharply lower on Tuesday with financial stocks bearing much of the damage as investors weighed the impact of harsh sanctions against Russia over its invasion of Ukraine.