george w. bush, puts a hard line conservative on the president's team just as he prepares to meet with north korea's kim jong-un. >> question. how do you know that the north korean regime is lying? answer, their lips are moving. >> reporter: he recently wrote that it would be "perfectly legitimate" for the u.s. to respond to north korea's nuclear build up by striking first. >> by striking first. jon karl with us live tonight from the white house. and jon, president trump is hoping to meet with kim jong-un by the end of may, and bolton is on the record before with what he thinks should happen in that meeting. >> reporter: he has said that the president should go into the meeting and tell kim jong-un simply, tell me you have begun total de-nuclearization because we're not going to have protracted negotiations. you can tell me that right now or we will start thinking of something else. so david, if he takes the advice of his new national security adviser, it could be a very short meeting with kim jong-un. >> jon karl at the white house. jon, thanks. all week, there were many closely watching the first lady