North Korea experts said they expect the missile launch, if it does occur, would come around around April 15, the day Kim Jong Un's grandfather, Kim Il Sung -- the founder of North Korea was born. The launch could be another test, or a military strike attempt, experts said.
April 15 is considered the most important holiday to North Koreans who have been celebrating it with bonus rations of meat and rice, and candy treats for children.
The U.S. and its allies in the region are weighing possible responses should a missile launch occur.
Retired Marine Corps Col. Steve Ganyard, an ABC News military consultant, said the U.S. has never attempted to shoot down a rocket similar to North Korea's.
"Until you actually do it for real there's no knowing that we have 100 percent certainty of knocking this down," Ganyard said.
ABC News' Luis E. Martinez and The Associated Press contributed to this report.