North Korea's underground nuclear test site has partially collapsed following a massive bomb blast last year, making it unusable, Chinese seismologists conclude.
The United States says that North Korea may be only months away from being able to strike the US mainland with a nuclear-tipped ballistic missile, while Pyongyang says Washington is considering a pre-emptive strike against it.
North Korea's underground nuclear test site has partially collapsed following a massive bomb blast last year, making it unusable, Chinese seismologists conclude.
The United States says that North Korea may be only months away from being able to strike the US mainland with a nuclear-tipped ballistic missile, while Pyongyang says Washington is considering a pre-emptive strike against it.
