US President Donald Trump and his Chinese counterpart Xi Jinping have agreed to halt new trade tariffs for 90 days to allow for talks. At a post-G20 summit meeting in Buenos Aires, Mr Trump agreed not to boost tariffs on $200bn (£157bn) of Chinese goods from 10% to 25% on 1 January, BBC reported.  China will buy a "very substantial" amount of agricultural, industrial and energy products, the BBC says.  Meanwhile, Beijing says the two sides agreed to open up their markets.  Mr Trump and Mr Xi held a "highly successful meeting ...