With U.S.-North Korea working-level talks finally in the books, Pyongyang is pushing the envelope even further with its missile testing -- sending a stronger message to Washington that progress in talks is critical to avoid a return to escalation. The twinning of the new threshold in missile testing with movement on working-level talks confirms that North Korea is sharpening the U.S. choice between breakthrough and breakdown, making clear that it is serious about its self-declared end-of-2019 deadline for progress in negotiations. ...