South Korean President Lee Myung-bak called for defense reform to build up military forces Saturday, while tension with North Korea continues. The reform focuses on giving the chairman of the Joint Chiefs of Staff more control over the army, navy and air force to make the military\'s command structure more efficient and help the armed forces better deal with North Korean assaults, Yonhap News Agency reported. North Korea\'s attacks on the South made it clear \"defense reform is an urgent task that cannot be delayed any longer,\" Lee said Saturday. South Korea blames North Korea for the sinking of a warship in March 2010 that killed 46 sailors. North Korea also fired on a South Korean border island in November, killing two soldiers and two civilians. Lee also said the military needs to see fundamental change before South Korea takes over wartime operational control from the United States in 2015. The United States has held wartime command of South Korean forces since the beginning of the Korean War in 1950. In a deal reached in 2007, South Korea was to take over control in April 2012, but after North Korea sunk the battleship, both sides agreed to push the power transfer to 2015.