Veteran US diplomat William Burns, nominated to lead the CIA, pledged Wednesday to keep the agency free of politics and said China would be his main focus if confirmed.  Burns also told the panel that China was the main challenge the country faces, echoing views stated by Biden and other top officials of his administration. Burns called Xi Jinping's approach an "aggressive, undisguised ambition and assertiveness" that must be faced down in a long-term effort, in conjunction with allies that Beijing lacks. If approved as expected by the Senate, Burns will be the first career diplomat to lead the CIA.