ultimately will be able to strike north korea. >> reporter: despite repeated pressure from the president and a recent diplomatic mission by china, kim jong-un has made it clear he is not backing down. instead, the north koreans have been accelerating every aspect of their weapons programs, testing a massive hydrogen bomb in september, fine-tuning their rocket fuels and engines, and honing their targeting and guidance systems. the u.s. believes kim and his generals could be able to place a miniaturized warhead on top of a missile sometime next year. experts say they're just a couple of steps away from demonstrating a full-fledged capability to hit the continental u.s. with a nuclear-tipped missile. >> the one thing they could do to demonstrate an end to end nuclear capability is to put an actual nuclear weapon on the top of a missile and fire it off into the pacific and actually detonate it out there somewhere. to get there, we think there might be a couple things to work out such as miniaturization and re-entry so that it actually gets through the atmosphere