North Korea has failed in its third attempt since 1998 to build an accurate long range missile, analysts say, undercutting its image as a defiant state able to project its power across the ocean.
The communist North claimed it had launched a satellite on Sunday that was now circling the globe, transmitting data and patriotic songs praising secretive leader Kim Jong-Il.
But the United States and South Korea say the launch failed to get anything into orbit, and experts said the rocket's second and third stages apparently did not separate as planned.
"(It) was a failure," Joseph Bermudez of Jane's Information Group told AFP.
"It seems to indicate that North Korea has not been able to demonstrate a reliable system capable of being an ICBM or a space launch vehicle."
Washington, Seoul and Tokyo said the launch was a smoke-screen for testing a Taepodong-2 intercontinental ballistic missile (ICBM), which at maximum range could theoretically hit the US states of Alaska and Hawaii.
Bermudez said current information indicated the second stage did not drop, meaning the rocket was too heavy to sustain flight.