north korea will blow up the u.s. mainland and annihilate americans. disturbing. thank you very much. north korea has evolved from a regional menace to global threat. strong words from the head of the u.n.'s international atomic energy agency. he called sunday's test of what pyongyang called a hydrogen bomb a new dimension of threat. for more on the diplomatic efforts to cool tensions on the spla, let's bring in -- peninsula, let's bring in nic robertson with more on what the head of the iaea told you. >> reporter: what i really wanted to frunderstand from his expertise is effectively north korea in a position of having a nuclear weapons system that can threaten the world as they say they can. his view is we can't say for