South Korea's point man on North Korea urged Pyongyang Thursday to give up its nuclear weapons programs and improve ties with Seoul. Unification Minister Ryoo Kihl-jae said the North's nuclear weapons won't help the communist country to revive its moribund economy and enhance the livelihoods of its 24 million people. "North Korea should lay down its nuclear weapons if it chooses to develop its economy," Ryoo said in a speech to his officials. "Then, North Korea can earn serious and sincere cooperation from us."    North Korea, which conducted three nuclear tests in recent years, has vowed to pursue both nuclear and economic development simultaneously. The North views its nuclear programs as a deterrent against what it claims is the United States' hostile policy against it. Ryoo also called on the North to grasp the hand of trust and cooperation extended by South Korea. His comments came a day after North Korean leader Kim Jong-un called for improving ties with South Korea in his New Year's message. Kim also vowed to make aggressive efforts to improve inter-Korean relations following months of tension. In December, North Korea warned of military strikes against 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. Kim's rare conciliatory gesture comes amid concerns of possible political unrest in North Korea following the execution of his once-powerful uncle, Jang Song-thaek, and his associates. Kim boasted during his speech that the purge has strengthened the party. Still, Ryoo said potential instability could persist in North Korea, noting the North can achieve stability only if it injects energy into the economy.