South Korea official : This would `` show off their two-way track capability , '' the official said . The North Korean government has been very open about its nuclear weapons program and the fact that it is developing a hydrogen bomb. Official : Tunnel closure is last step to ready for test . Details come as U.S. President Obama visits South Korea .
South Korea official : The North Korean government has been very open about its nuclear weapons program and the fact that it is developing a hydrogen bomb. Official : Tunnel closure is last step to ready for test . Details come as U.S. President Obama visits South Korea .