The world’s financial leaders rejected protectionism on Tuesday and urged “further dialogue” on trade, but failed to diffuse the threat of a trade war days before U.S. metals tariffs take effect and Washington is to announce measures against China. Finance ministers and central bankers of the world’s 20 biggest economies, which represent 75% of world trade and 85% of global gross domestic product, discussed trade disruptions as a risk to growth at a two-day meeting.