North Korean leader Kim Jong-un called Wednesday for improved ties with South Korea while vowing to strengthen military capabilities in the New Year, a policy that may defy outside pressure to give up nuclear weapons under his control. In a New Year's message delivered live on the North's television and radio, the 30-something leader also vowed to rebuild the North's moribund economy in the New Year with emphasis on increasing food production. "We will make aggressive efforts to improve relations between the North and the South,” Kim said in the speech which lasted 25 minutes. "The South side should also come forward to improve relations between the North and the South.” His comment came days amid concerns that the North may stage provocations against South Korea as part of its strategy to forge internal unity following the execution of Kim's once-powerful uncle, Jang Song-thaek, on charges of treason. The high-profile purge of Jang, who had long been considered the North's No. 2 man and Kim's regent, sparked concerns over potential instability in the isolated country. Kim made no direct mention of Jang's purge in the speech, saying only that "the purge of anti-party and anti-revolutionary faction has strengthened the party."    Without naming Jang, the leader called him a "factional rubbish."    North Korea has a track record of carrying out provocations at a time of its internal instability in an apparent attempt to divert people's attention and forge unity. In December, North Korea threatened to strike South Korea in anger over a Seoul rally, in which conservative protesters burned effigies of Kim and his father and grandfather, the North's two late leaders, Kim Jong-il and Kim Il-sung. The South Korean capital city of Seoul, with more than 10 million people, is within the range of North Korea's conventional artillery positioned along their heavily fortified border. Seoul has repeatedly vowed to retaliate against any provocations to avenge the deaths of 50 South Koreans who were killed in North Korea's two separate attacks in March and November of 2010.