By Phil Stewart and David Alexander
WASHINGTON (Reuters) - 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 February 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.
U.S. SAYS SYSTEMS NOT AIMED AT CHINA OR RUSSIA
U.S. officials say its missile defense systems are not designed to counter the large number of ICBMs in arsenals in China or Russia and are focused instead on the threat from North Korea or, potentially, Iran.
Friday's announcement came with a key caveat - the Pentagon said it would only buy the extra interceptors if they perform appropriately in tests. The interceptors in question have not hit a target since 2008, a defense official said.
Boeing Co. is the prime contractor of the system. Key Boeing subcontractors include Raytheon Co., which makes the kill vehicle, and Orbital Sciences Corp, which makes the rocket booster.
Admiral James Winnefeld, vice chairman of the U.S. military's Joint Chiefs of Staff, expressed confidence in the missiles and said he believed the steps taken by the United States would make North Korea's young leader, Kim Jung-un, think twice before acting on bellicose rhetoric.
"We not only intend to put the mechanics in place to deny any potential North Korean objective to launch a missile to the United States, but also to impose costs on them if they do," he told reporters.
"And we believe that this young lad ought to be deterred by that. And if he's not, we'll be ready."
Lee Jong-won, an expert on North Korea at Japan's Waseda University, said the planned missile deployment could trigger unpredictable behavior from Pyongyang.
"With the measures the United States has announced, the North is likely to object even more ... The North's objections could escalate," Lee said.
The addition of another 14 interceptors amounts to a reversal of an Obama administration decision in 2010 to stop expansion of the missile interceptor system at 30. The Bush administration had planned to deploy a total of 44.
The United States currently has 26 interceptors deployed at Fort Greely and four at Vandenberg Air Force Base in California.
Congressman Mike Turner, chairman of the House Armed Services Subcommittee on Tactical Air and Land Forces, said the Obama administration had began "to realize the shortcomings of its missile defense strategy."
"Now that the administration has decided to see clearly, America can get back on the right course," Howard McKeon, chairman of the House Armed Services Committee, said in a statement, lamenting lost time and resources.
In a sign of fiscal pressures facing the Pentagon, U.S. officials acknowledged they were also forgoing development of a new anti-missile interceptor that would have been deployed in Europe. They said European defense would be unaffected.
Officials said the United States would move forward with congressionally mandated environmental impact studies for alternative sites in the United States for deploying additional ground-based interceptors, if needed.
Winnefeld said locations on the East Coast were being considered but declined to offer details.
"We're still looking at sites," he said.
(Additional reporting by Ben Blanchard in Beijing and Yoko Kubota in Tokyo; Editing by Mohammad Zargham, David Brunnstrom and Dean Yates)