Wall Street battered as Treasury chief fails to reassure

Wall Street shares plunged for a fourth straight session Monday as investors panned Treasury Secretary Steven Mnuchin's efforts to try to reassure markets.Mnuchin on Sunday held a phone call with the six biggest US banks, reporting on Twitter that the CEOs have "ample liquidity" available.The broad-based S&P 500 finished down 2.7 percent, a bitter finale to the lead-up to Tuesday's Christmas holiday, when markets will be closed.