SEOUL, Korea, Republic Of -- South Korea warned on Wednesday of "searing" consequences if North Korea doesn't abandon plans to launch a long-range rocket that critics call a banned test of ballistic missile technology.

The South's rhetoric about unspecified harsh consequences comes less than a month after the North's defiant fourth nuclear test and as diplomats at the U.N. work on strong new sanctions against Pyongyang.

North Korea on Tuesday informed international organizations of its plans to launch an Earth observation satellite on a rocket between Feb. 8 and 25, and if North Korea's past patterns are any clue, angry warnings by its neighbours and Washington probably won't dissuade a coming launch.

The launch declaration, which is meant to warn civilians, shipping and aircraft in the area about the rocket and falling debris, follows North Korea's disputed claim on Jan. 6 to have tested a hydrogen bomb, the country's fourth nuclear test. A launch would be seen as a snub by North Korea of its only major ally, China, whose representative for Korean affairs landed in Pyongyang for talks on Tuesday.

South Korean and U.S. officials said the launch would threaten regional security and violate U.N. Security Council resolutions that ban the country from engaging in any ballistic activities.

"We warn that if North Korea proceeds with a long-range missile launch, the international society will ensure that the North pays searing consequences for it as the launch would constitute a grave threat to the Korean Peninsula, the region and the world," senior South Korean presidential official Cho Tae-yong said in televised remarks.

In Washington, Daniel Russel, the top diplomat for East Asia, said the U.S. was tracking reports of the North's planned launch. He said a launch that uses ballistic missile technology would be another violation of a U.N. ban and strengthens the argument for the international community to impose "real consequences" on North Korea for destabilizing behaviour. He called for the imposition of tough additional sanctions.

Russel said a launch "would be an unmistakable slap in face to those who argue that you just need to show patience and dialogue with the North Koreans but not sanctions," in an apparent reference to China.

North Korea has spent decades trying to develop operational nuclear weapons along with missiles capable of striking the mainland United States.

North Korea's last long-range rocket launch, in December 2012, was seen as having successfully put the country's first satellite into orbit after a string of failures. The North also told international agencies before that launch of its plans. Each new rocket launch improves North Korea's missile technology, which is crucial for its goal of developing a nuclear-armed missile capable of hitting the U.S. mainland.

U.N. deputy spokesman Farhan Haq said North Korea informed the International Civil Aviation Organization and the International Telecommunication Union of its launch plans.

"Right now, we're carefully monitoring developments and are in close touch with the interested parties and the international organizations," Haq said at U.N. headquarters in New York.

The International Telecommunication Union said North Korea informed its Geneva office of its intention to launch a Kwangmyongsong (Bright Star) -type Earth observation satellite with a four-year operational life. But the ITU's U.N. representative, Gary Fowlie, said not enough technical information had been supplied to register the planned launch in its Master International Frequency Register.

A South Korean official, who spoke on condition of anonymity because of office rules, said Seoul estimated that the first stage of the rocket would fall off the west coast of South Korea, more debris would land near the South's Jeju Island, and the second stage would land off the Philippines' east coast.

North Korea, an autocracy run by the same family since 1948, is estimated to have a handful of crude nuclear devices and an impressive array of short- and medium-range missiles, but it closely guards details about its nuclear and missile programs. This means there is considerable debate about whether it can produce nuclear bombs small enough to place on a missile, or missiles that can reliably deliver their bombs to faraway targets.

The North's recent nuclear test has led to another push in the U.N. to tighten sanctions, something that followed North Korea's 2012 rocket launch and its 2013 third nuclear test. The North followed that test with an escalating campaign of bombast that included threats to fire nuclear missiles at the United States and South Korea.

North Korea has said that plutonium and highly enriched uranium facilities at its main Nyongbyon nuclear complex are in operation. But just what is happening at Nyongbyon is unclear. North Korea booted out international inspectors in 2009, and independent assessments by outside experts since then have been spotty.


Associated Press writers Foster Klug in Seoul, South Korea, Edith M. Lederer at the United Nations and Matthew Pennington in Washington contributed to this report.