North Korea's communist regime has warned of a nuclear war on the Korean peninsula while vowing to step up its atomic bomb-making program in defiance of new UN sanctions. In a commentary published Saturday and seen in Seoul on Sunday, the state-run Tongil Sinbo weekly claimed the US has been deploying a vast amount of nuclear weapons in South Korea and Japan, and that they are ready to be used against the North. North Korea "is completely within the range of US nuclear attack and the Korean peninsula is becoming an area where the chances of a nuclear war are the highest in the world," the commentary said. The North's continued defiance presents a new diplomatic headache for US President Barack Obama as he prepares for talks Tuesday with his South Korean counterpart on the North's missile and nuclear programs. Kim Yong-kyu, a spokesman at the US military command in Seoul, called the latest accusation "baseless," saying Washington has no nuclear bombs in South Korea. US tactical nuclear weapons were removed from South Korea in 1991 as part of arms reductions following the Cold War. Also Saturday, North Korea's Foreign Ministry threatened war on any country that dared to stop its ships on the high seas under the new sanctions approved by the UN Security Council on Friday as punishment for the North's latest nuclear test. It is not clear if the statements are simply rhetorical. Still, they are a huge setback for international attempts to rein in North Korea's nuclear ambitions, which received a boost with its second nuclear test on May 25. It first tested a nuclear device in 2006. In its statement Saturday, North Korea said it has been enriching uranium to provide fuel for its light-water reactor. It was the first public acknowledgment the North is running a secret uranium enrichment program in addition to its known plutonium-based program. The two radioactive materials are key ingredients in making atomic bombs. On Sunday, Yonhap news agency reported South Korea and the US have mobilized spy satellites, reconnaissance aircraft and human intelligence networks to obtain evidence that the North has been running a uranium enrichment program. South Korea's Defense Ministry said it cannot confirm the report. The National Intelligence Service - South Korea's main spy agency - was not available for comment. North Korea said more than one-third of 8,000 spent fuel rods in its possession has been reprocessed and all the plutonium extracted would be used to make atomic bombs. The country could harvest 13-18 pounds (6-8 kilograms) of plutonium - enough to make at least one nuclear bomb - if all the rods are reprocessed. In addition, North Korea is believed to have enough plutonium for at least half a dozen atomic bombs. North Korea says its nuclear program is a deterrent against the US, which it routinely accuses of plotting to topple its regime. Washington, which has 28,500 troops in South Korea, has repeatedly said it has no such intention. The new UN sanctions are aimed at depriving the North of the financing used to build its rogue nuclear program. The resolution also authorized searches of North Korean ships suspected of transporting illicit ballistic missile and nuclear materials. US Secretary of State Hillary Rodham Clinton said the new UN penalties provide the necessary tools to help check North Korea's continued pursuit of nuclear weapons. The sanctions show that "North Korea's pursuit of nuclear weapons and the capacity to deliver those weapons through missiles is not going to be accepted by the neighbors as well as the greater international community," Clinton said Saturday at a news conference in Canada.