North Korea will have a nuclear missile able to reach California in 2018

North Korea should be able to finish a missile that can reach the continental United States within one year, according to several administration officials briefed on the new assessment by US Intelligence agencies.

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.

Quietly, the Pentagon has been refining longstanding contingency plans, from intercepting missile parts at sea to attempting, if Mr. Trump should decide to do it, to destroy a missile on the launchpad, before it is tested. But it is more likely that the United States would first try a variant of the effort developed during the Obama administration to sabotage the launches with cyber and electronic warfare techniques, and with a steady flow of bad parts.