North Korean leader Kim Jong-un has vowed to bolster the country's nuclear capabilities to deter any threats by enemies, saying it is steadily carrying out a policy to increase the number of nuclear weapons exponentially, state media said Tuesday.Kim made the vow during a speech in a meeting with senior party and government officials on the occasion of the 76th founding anniversary of the regime, according to the Korean Central News Agency (KCNA).He said the U.S.-led move to expand a military bloc in the region has posed a grave security threat to North Korea and raised the need for his country to bolster its nuclear arsenal."The obvious conclusion is that the nuclear force of the DPRK and the posture capable of properly using it for ensuring the state's right to security in any time should be more thoroughly perfected," Kim said, using the acronym of the North's official name, the Democratic People's Republic of Korea.Source: Yonhap News Agency