Beijing in November declared its Air Defense Identification Zone in the East China Sea extended over islands disputed with Japan and a reef disputed with South Korea. China demanded that all aircraft intending to enter the zone first submit a flight plan and Chinese officials reserves the right to deny access. China has dismissed calls by officials in Washington, Tokyo and Seoul to roll back the defense zone, which it calls legal and within its rights. U.S. Vice President Joe Biden also rejected the self-declared aviation security, saying it raises tensions in the region and the possibility of miscalculation. Biden made the comments while in South Korea where he reaffirmed a U.S. plan to re-focus on the Asia Pacific and urged North Korea to give up its nuclear weapons