london north korea continue regularly test missiles military action unite state would prompt war senior north korean official tell bbc monday north korea conduct several missile nuclear test defiance u.n. sanction say develop missile strike u.s. mainland late missile test sunday fail second launch u.s. vice president mike pence warn north korea monday recent u.s. strike syria one pyongyang close ally afghanistan show resolve president donald trump test conduct missile test weekly monthly yearly basis bbc quote vice foreign minister han song-ryol say interview u.s. reckless enough use military mean would mean day war north korean state media last week warn nuclear attack unite state sign american aggression white house say evidence possess capability bbc report han also say north korea believe nuclear weapons protect threat military action unite state north korean official say continue missile test bbc