Japan continued to see the importance of the US military presence in the region, according to a Defense White Paper approved by the cabinet. The relocation of the US airbase in Okinawa has been a thorn in the side of the Democratic Party of Japan-led government but the White Paper justified its presence and stressed on the importance of regional security. The 2010 Defense White Paper explained the US presence is important to Japan due to North Korea's increasing threat. Pyongyang has been increasing its ballistic missile capability and promoting weapons of mass destruction. China's military build up was also being looked on with concern. During the past months, there have been reports of China's naval vessels and submarines in waters close to Japan's southern islands. The Defence Paper also said that the two countries are in the process of deepening ties commemorating the 50th anniversary of the conclusion of the current bilateral security agreement. US-Japan ties have been tense since the Democratic Party of Japan won the general election last year.