North Korea's most advanced long-range missile is being assembled at a launch site for a possible test-firing later this month, a newspaper said. Washington urged Pyongyang not to take any "provocative" actions that could undermine peace efforts. The Taepodong-2 missile has recently been moved to the Musudan-ni site on the North's eastern seaboard, but it has not yet been seen near the launch pad, South Korea's mass-circulation Chosun Ilbo reported Friday. "We assume that they are currently assembling the first- and second-stage rockets," the newspaper quoted an unidentified South Korean government official as saying. South Korean and American intelligence authorities believe the North could test-fire the missile, potentially capable of reaching the western US, around Feb. 25, the first anniversary of South Korean President Lee Myung-bak's inauguration, the newspaper said. The National Intelligence Service, Seoul's top spy agency, said it could not confirm the report, citing the sensitivity of intelligence matters. Separately, the North warned the South against violating the countries' disputed western maritime border, a key flash point. The North doesn't recognize the border demarcated by the United Nations at the end of the 1950-53 Korean War and says it should be redrawn farther south. South Korea rejects the North's demand. The dispute led to deadly naval skirmishes in the area in 1999 and 2002. If South Korea "encroaches even an inch of our sacred territorial waters," North Korean troops will "put warmongers into the West sea," the North's main Rodong Sinmun newspaper said Friday. North Korea's saber-rattling has been interpreted as an attempt to grab President Barack Obama's attention, though his defense secretary, Robert Gates, has played down reports of possible missile launch preparations, noting Tuesday that the North's last such test in 2006 was a failure. Seoul and Washington have issued repeated warnings to North Korea over a possible launch, with new South Korean Unification Minister Hyun In-taek telling lawmakers Friday that the North should not fire a missile and that Seoul will "sternly deal" with any provocation. In New York, US Secretary of State Hillary Rodham Clinton urged North Korea on Friday not to take any provocative actions, and she reiterated Washington's willingness to normalize ties in return for nuclear disarmament. "It is incumbent on North Korea to avoid any provocative action and unhelpful rhetoric toward South Korea," said Clinton, speaking to the Asia Society on the eve of a trip to Japan, Indonesia, South Korea and China - her first in her new job. Clinton also suggested the US could sign a peace treaty to formally end the Korean War. The 1950-53 conflict ended with a truce. "If North Korea is genuinely prepared to completely and verifiably eliminate their nuclear weapons program, the Obama administration will be willing to normalize bilateral relations, replace the peninsula's long-standing armistice agreements with a permanent peace treaty and assist in meeting the energy and other economic needs of the North Korean people," Clinton said.