The last time presidents Donald Trump and Xi Jinping met, they emerged optimistic, even without a formal deal. Their reunion on Thursday comes with much more at stake: China’s grip on the rare earths needed to keep US factories, advanced technology and defence production running.The leaders of the world’s two largest economies reconvene at the White House with trade, artificial intelligence and the war in Iran on the agenda. But looming over the talks is Beijing’s dominance of critical minerals and its willingness to restrict their supply as economic leverage.in April last year, China enforced strict controls on certain types…