seoul north korea say new intercontinental ballistic missile icbm test-fired wednesday launch newly develop vehicle warhead could withstand pressure re-enter earth atmosphere north korean leader kim jong un personally guide missile test say new launcher impeccable state media say describe new vehicle breakthrough observers analysts cast doubt north korea ability master technology need design warhead capable withstand enormous pressure re-entry earth atmosphere suggest isolate country may still years away develop credible delivery vehicle nuclear weapon wednesday launch re-confirmed safety warhead atmospheric re-entry environment state media say without elaborate north korea say icbm test use new launch vehicle show successful warhead re-entry