The North maintains that it is launching a satellite. However, the U.S. and others say they are testing missile systems for nuclear weapons.
They are vowing to move ahead with the launch scheduled for mid April despite global warnings regarding a United Nations violation.
North Korea announced plans last month to launch an observation satellite using a three-stage rocket during celebrations of the 100th anniversary of the birth of North Korean founder Kim Il Sung.The U.S., Japan, Britain and other nations have urged North Korea to cancel the launch, warning that firing the long-range rocket would go against North Korea's promise to refrain from engaging in nuclear and missile activity.
North Korea maintains that the launch is a scientific achievement intended to improve the nation's faltering economy by providing detailed surveys of the countryside.
Experts say the Unha-3 rocket slated for liftoff between April 12 and 16 could also test long-range missile technology that might be used to strike the U.S. and other targets.
North Korea has tested two atomic devices, but is not believed to have mastered the technology needed to mount a warhead on a long-range missile.
The Associated Press contributed to this report.