U.S. Defense Secretary Chuck Hagel announced plans on Friday to bolster U.S. missile defenses in response to "irresponsible and reckless provocations" by North Korea, which threatened a preemptive nuclear strike against the United States last week.
Hagel said the Pentagon would add 14 new anti-missile interceptors at Fort Greely in Alaska - an effective reversal of an early Obama administration decision - and move ahead with the deployment of a second missile-defense radar in Japan.
The Pentagon also left open the possibility of creating a site on the U.S. East Coast where the Pentagon could field more interceptors capable of striking down an incoming missile. The 14 additional interceptor deployments would cost nearly $1 billion and must be approved by Congress.
"By taking the steps I outlined today we will strengthen our homeland defense, maintain our commitments to our allies and partners, and make clear to the world that the United States stands firm against aggression," Hagel told a news conference.
North Korea issued its threat last week to stage a preemptive nuclear attack against the United States as the United Nations readied new sanctions against Pyongyang in response to its Feb. 12 nuclear test, the country's third.
Experts say North Korea is years away from being able to hit the continental United States with a nuclear weapon, despite having worked for decades to achieve a nuclear capability.
But Hagel said the moves announced by the Pentagon were justified to stay ahead of the threat, underscored by the nuclear test and a December rocket launch that analysts believe was aimed at developing technology for an intercontinental ballistic missile (ICBM).
Hagel also cited North Korea's display last April of what appeared to be a road-mobile ICBM.
The Pentagon said the United States had informed China, North Korea's neighbor and closest ally, of its decision to add more interceptors but declined to characterize Beijing's reaction.
China has expressed unease at previous U.S. plans for missile defense systems, as well as sales of such systems to Taiwan and Japan, viewing it as part of Washington's attempt to "encircle" and contain China despite U.S. efforts to ease Chinese fears.
China has responded by developing an anti-missile system of its own, announcing the latest successful test in January.