washington democratic u.s. senators introduce bill tuesday say would prevent president donald trump launch nuclear first strike north korea highlight issue days republican first presidential trip asia measure would stop trump u.s. president launch attack north korea spend money military strike without congressional approval unless north korea first attack unite state tensions washington pyongyang build series nuclear missile test north korea bellicose verbal exchange trump north korean leader kim jong un cia say north korea could months away develop ability hit unite state nuclear weapon scenario trump vow prevent worry president enthusiasm check advisers around democratic senator chris murphy legislation lead sponsor tell reporters conference call republicans also express concern trump rhetoric none co-sponsored bill back seven democrats senator bernie sanders independent republicans control majorities senate house indication congressional leaders would allow vote similar measure introduce early year also fail advance however backers say might try pass late year introduce amendment legislation must-pass spend bill confidence come vote floor senate would prevail murphy say lawmakers try take back control foreign policy white house congress pass bill july bar president lift sanction russia without lawmakers approval senate foreign relations committee monday hold hear new authorization use military force aumf exert authority campaign islamic state militant group hear secretary state rex tillerson secretary defense jim mattis say trump authority use force north korea without imminent threat define threat would democrats want law stop trump bomb north korea