By Trevor Hunnicutt, David Brunnstrom and Michael Martina WASHINGTON (Reuters) -White House officials are gearing up for a virtual meeting between President Joe Biden and Chinese leader Xi Jinping they hope will show the world Washington can responsibly manage relations between the rival superpowers, people familiar with the matter say. Combative diplomatic exchanges with China early in the Biden administration unnerved allies and U.S. officials believe direct engagement with Xi, who has consolidated power in Beijing to a degree not seen since Mao Zedong, is the best way to prevent the relatio…