Until a few weeks ago, the official estimate was that it would take roughly four years, give or take 12 months, for North Korea to develop a missile that could carry a nuclear weapon small enough to fit into the missile's warhead and capable of surviving the stresses of re-entry and deliver it to the United States.

But the realities of the past few months, especially a July 4 test that crossed a major threshold — if just barely — has forced intelligence experts to conclude that their estimates have been too conservative.

If the 2018 estimate is right, North Korea will have a crude capability to reach the continental United States before the nation's missile defenses are upgraded.