South Korea says debris from a rocket fired by the North this month shows Pyongyang has significantly advanced it ballistic missile technology.

South Korean Defense Ministry officials said Sunday their reclusive North Korean neighbor has developed a rocket that has a range of more than 10,000 kilometers, if it were to carry a warhead of 500 to 600 kilograms. Authorities say the tested missile's range would allow it to reach the U.S. West Coast.

However, South Korean officials say it is not likely North Korea has developed the technology to miniaturize a nuclear bomb to mount on a missile.

North Korea says the rocket launch on December 12 was to put a weather satellite into orbit, denying it had any intent beyond peaceful purposes.

On Friday, North Korean leader Kim Jong Un called for the advancement of North Korean rockets while speaking at a banquet for rocket scientists in Pyongyang.

The U.S., South Korea, Japan and other governments have condemned the recent North Korean launch as a ballistic missile test banned under U.N. Security Council resolutions. But the North Korean leader has praised the launch as an unprecedented enhancement.

The timing of the launch surprised many observers and Western diplomats because reports, just a day earlier, suggested North Korea was disassembling the rocket because of technical difficulties.