hands on a nuclear bomb or nuclear material, they most certainly would use it to kill as many innocent people as possible. >> reporter: u.s. intelligence does not believe isis has the capability to build a nuclear warhead, but it could steal one, hijack a nuclear facility, or craft a so-called dirty bomb with materials small enough to fit in a coke can. laura holgate is the senior adviser to the president. >> that's more of a-- a contamination issue than it is an immediate loss of human life. but the effects of a dirty bomb in a facility could be-- in an urban center, could be, how long it takes to clean up, what kind of public panic that might engender. >> reporter: there have been over 2,500 incidents of nuclear material theft or unauthorized activity in the past 20 years. the white house wants to reduce global stockpiles of nuclear weapons and secure atomic material at energy plants, hospitals, and universities. now, world leaders asked the president about donald trump's