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The usually all-business G20 summit in Argentina is likely to be overshadowed by a range of sensitive diplomatic situations - many of them involving President Donald Trump. The G20 makes up 19 of the world's top economies plus the European Union - they begin two days of talks on Saturday (NZ time). Mr Trump has caused tensions with China over trade, Russia over election campaign links, Mexico over immigration and he's weighed in on Brexit. In the past few hours, he's cancelled a meeting with Russian president Vladimir Putin because of Russia's dispute with Ukraine over Crimea. Our correspondent in Buenos Aires is Tim Willcox. He talks to Guyon Espiner.