South Korea's Defense Ministry says North Korea could fire a missile any day.
U.S. officials agree that a missile is fueled and ready for launch, but the target is unknown.
In a recent Senate hearing, Admiral Samuel Locklear, commander of the U.S. Pacific Command, said the United States is ready to shoot down a missile if necessary.
When asked by Sen. John McCain, R-Ariz., if he would recommend such an action, Locklear replied, "If the missile was in the defense of the homeland, I would certainly recommend that action. And if it were in defense of our allies I would recommend that action."
Meanwhile, the South Korean government is on high alert, a threat level just short of war.
It says Kim Jong Un's regime is just blustering, but military officials say that the young leader is much more unpredictable than his father or grandfather.