North Korea, celebrating the birthday of reclusive leader Kim Jong Il, vowed Monday to carry out what experts said would be a test-firing of its longest-range missile. South Korea's foreign minister cautioned against any kind of launch, while U.S. Secretary of State Hillary Rodham Clinton urged the country to follow through on abandoning its nuclear weapons program. "One will come to know later what will be launched" from North Korea, the official Korean Central News Agency said in a dispatch from Pyongyang. North Korea claimed that the U.S. and other countries were spreading rumors about "preparations for launching a long-distance missile" and said it has the right to pursue "space development" - a term the country has used in the past to disguise a missile test as a satellite launch. It also accused the United States and other countries of trying to block the country's "peaceful scientific research" by linking it to a missile test.