LONDON (Reuters) - World stocks hit their highest in almost two years on Tuesday, keeping record highs in sight, following fresh signs that the United States and China were working to end a bitter trade war that has dealt a blow to the global economy. China's Vice Premier Liu He, U.S. Trade representative Robert Lighthizer and U.S. Treasury Secretary Steven Mnuchin held a phone call on issues related to a phase one trade agreement on Tuesday, China's commerce ministry said.This, alongside a..