any action, that north korea may take or any provocation. >> reporter: the joint chiefs chairman, offering a grim assessment of how close north korea is to putting a nuclear warhead on a missile, a direct threat to the u.s. >> in the absence of concrete evidence to the contrary, we have to assume the worst case. >> reporter: u.s. intelligence indicates the regime in the last few days may have used several short-range missile launchers around the country. that's on top of the two intermediate-range mobile missiles it parked along its east coast. the u.s. worries multiple missile launches are the first of more provocative actions by the north. no one has forgotten the 2010 shelling of a south korean island by north korea. >> we may see a succession of things to try to make this point that they are a strong and prosperous nation.