The U.S. is planning a major expansion of missile defenses in Asia, a move American officials say is designed to contain threats from North Korea, but one that could also be used to counter China's military.
The planned buildup is part of a defensive array that could cover large swaths of Asia, with a new radar in southern Japan and possibly another in Southeast Asia tied to missile-defense ships and land-based interceptors.
It is part of the Obama administration's new defense strategy to shift resources to an Asian-Pacific region critical to the U.S. economy after a decade of war in Iraq and Afghanistan.
The expansion comes at a time when the U.S. and its allies in the region voice growing alarm about a North Korean missile threat. They are also increasingly worried about China's aggressive stance in disputed waters such the South China Sea, where Asian rivals are vying for control of oil and mineral rights.
U.S. defense planners are particularly concerned about China's development of antiship ballistic missiles that could threaten the Navy's fleet of aircraft carriers, critical to the U.S. projection of power in Asia.
"The focus of our rhetoric is North Korea," said Steven Hildreth, a missile-defense expert with the Congressional Research Service, an advisory arm of Congress. "The reality is that we're also looking longer term at the elephant in the room, which is China."
China's Ministry of National Defense didn't comment directly on the anti-missile plans, but sounded a cautious note.
"China has always believed that anti-missile issues should be handled with great discretion, from the perspective of protecting global strategic stability and promoting strategic mutual trust among all countries," it said in a statement on Thursday. "We advocate that all parties fully respect and be mindful of the security concerns of one another and try to realize overall safety through mutual benefit and win-win efforts, while avoiding the situation in which one country tries to let its own state security take priority over other countries' national security."
In a separate statement, China's Foreign Ministry said it hopes the U.S. "will carefully handle this problem out of concern for maintaining the global and regional strategic balance and stability, and promoting the strategic mutual trust among all countries."
A centerpiece of the new effort would be the deployment of a powerful early-warning radar, known as an X-Band, on an undisclosed southern Japanese island, said U.S. defense officials. The Pentagon is discussing that prospect with Japan, one of Washington's closest regional allies. The radar could be installed within months of Japan's agreement, American officials said, and would supplement an X-Band the U.S. positioned in Aomori Prefecture in northern Japan in 2006.
A Japanese Ministry of Defense spokesman said the government wouldn't comment. The U.S. and Japan have ruled out deploying the new radar to Okinawa, a southern island whose residents have long chafed at the U.S. military forces' presence there.
Officials with the U.S. military's Pacific Command and Missile Defense Agency have also been evaluating sites in Southeast Asia for a third X-Band radar to create an arc that would allow the U.S. and its regional allies to more accurately track any ballistic missiles launched from North Korea, as well as from parts of China.
Some U.S. defense officials have focused on the Philippines as the potential site for the third X-Band, which is manufactured by Raytheon Co. Pentagon officials said a location has yet to be determined and that discussions are at an early stage.
The beefed-up U.S. presence will likely raise tensions with the Chinese, who have been sharp critics of U.S. ballistic missile defenses in the past. Beijing fears such a system, similar to one the U.S. is deploying in the Middle East and Europe to counter Iran, could diminish China's strategic deterrent. Beijing objected to the U.S.'s first X-Band deployment in Japan in 2006. Moscow has voiced similar concerns about the system in Europe and the Middle East.
Without commenting on specific plans, Pentagon Press Secretary George Little said: "North Korea is the immediate threat that is driving our missile defense decision making."
In April, North Korea launched a multistage rocket that blew up less than two minutes into its flight. It conducted previous launches in August 1998, July 2006 and April 2009.
The Pentagon sent a sea-based X-Band, normally docked in Pearl Harbor, to the Pacific to monitor the most recent North Korean launch as a precaution.
The Pentagon is particularly concerned about the growing imbalance of power across the Taiwan Strait. China has been developing advanced ballistic missiles and antiship ballistic missiles that could target U.S. naval forces in the region.
China has between 1,000 and 1,200 short-range ballistic missiles aimed at Taiwan, and has been developing longer range cruise and ballistic missiles, including one designed to hit a moving ship more than 930 miles away, says the Pentagon's latest annual report on China's military.
The proposed X-Band arc would allow the U.S. to not only cover all of North Korea, but to peer deeper into China, say current and former U.S. officials.
"Physics is physics," a senior U.S. official said. "You're either blocking North Korea and China or you're not blocking either of them."
Beijing has said it poses no threat to its neighbors.
One goal of the Pentagon is to reassure its anxious regional allies, which are walking a fine line. Many want the U.S.'s backing but also don't want to provoke China, and they aren't sure Washington can counter Beijing's rapid military modernization because of America's fiscal constraints.
U.S. Defense Secretary Leon Panetta said during a visit Wednesday to the USS John C. Stennis warship in Washington state that the U.S. would "focus and project our force into the Pacific."
The U.S. presence on the ground in Asia, especially the Marine bases in Okinawa, has been a source of constant tension, and a more determined presence could spark similar problems. In addition to the new X-Band site in southern Japan, the U.S. plans to increase the number of Marines in Okinawa in the near term before relocating them to Guam. As the Marines are pulled out of Afghanistan, going from 21,000 to less than 7,000, the number of forces on Okinawa will rise, from about 15,000 to 19,000, officials said.
Analysts say it is unclear how effective U.S. missile defenses would be against China. A 2010 Pentagon report on ballistic missile defenses said the system can't cope with large-scale Russian or Chinese missile attacks and isn't intended to affect the strategic balance with those countries.
The senior U.S. official said the new missile defense deployments would be able to track and repulse at least a limited strike from China, potentially enough to deter Beijing from attempting an attack.
Jeffrey Lewis, director of the East Asia nonproliferation program at the Monterey Institute of International Studies in California, said any missile-defense deployments in the Asian theater will alarm the Chinese, particular if they believe the systems are designed to cover Taiwan. "If you're putting one in southern Japan and one in the Philippines, you're sort of bracketing Taiwan," Mr. Lewis said. "So it does look like you're making sure that you can put a missile defense cap over the Taiwanese."
Mr. Hildreth of the Congressional Research Service said the U.S. was "laying the foundations" for a regionwide missile defense system that would combine U.S. ballistic missile defenses with those of regional powers, particularly Japan, South Korea and Australia.
U.S. officials say some of these allies have, until now, resisted sharing real-time intelligence, complicating U.S. efforts. Territorial disputes between South Korea and Japan have flared anew in recent weeks, underlining the challenge of creating unified command and control systems that would be used to shoot down incoming missiles.
The U.S. has faced a similar problem building an integrated missile-defense system in the Persian Gulf.
Once an X-Band identifies a missile's trajectory, the U.S. can deploy ship-or-land-based missile interceptors or antimissile systems.
The Navy has drawn up plans to expand its fleet of ballistic missile-defense-capable warships from 26 ships today to 36 by 2018, according to Navy officials and the Congressional Research Service. Officials said as many as 60% of those are likely to be deployed to Asia and the Pacific.
In addition, the U.S. Army is considering acquiring additional Terminal High Altitude Area Defense, or THAAD, antimissile systems, said a senior defense official. Under current plans, the Army is building six THAADs.