By Andrea Shalal & David Brunnstrom
North Korea's latest rocket launch may kick off a rapid buildup of US missile defences in Asia, according to US officials and missile defence experts, something that could further strain ties between the United States and China.
North Korea says it put a satellite into orbit yesterday, but the United States and its allies see the launch as cover for Pyongyang's development of ballistic missile technology that could be used to deliver a nuclear weapon.
Washington vowed to ensure that the United Nations Security Council imposed serious consequences on Pyongyang after the launch, which followed a January 6 North Korean nuclear test, and sought to reassure its allies South Korea and Japan of its ironclad commitment to defending the region.
The United States and South Korea issued a joint statement just hours after the launch saying they would begin formal discussions about deploying the sophisticated Terminal High Altitude Area Defense system (THAAD) to the Korean peninsula "at the earliest possible date."
South Korea had been reluctant to discuss openly the possibility of deploying THAAD due to worries about upsetting China, its biggest trading partner.
Beijing, at odds with the United States over Washington's reaction to its building of artificial islands in the disputed South China Sea, has expressed "deep concern" about a system whose radar could penetrate its territory.
Russia has also raised concerns about increased US missile defence assets in Asia.
But the North Korean rocket launch, on top of last month's nuclear test, could be a "tipping point" for South Korea and win over parts of Seoul's political establishment that remain wary of such a move, a US official said.
South Korea and the United States said that if THAAD was deployed to South Korea, it would be focused only on North Korea.
Washington moved one of its five THAAD systems to Guam in 2013 following North Korean threats, and is now studying the possibility of converting a Hawaii test site for a land-based version of the shipboard Aegis missile defence system into a combat-ready facility.
Japanese Defense Minister Gen Nakatani said in November that Tokyo would consider deploying THAAD to bolster ballistic missile defences.
Japanese officials could not immediately be reached for comment on whether Tokyo would now seek a THAAD system after North Korea's rocket flew over Japan's southern Okinawa prefecture.
Some experts questioned how effective THAAD would be against the type of long-range rocket launched by North Korea and the Pentagon concedes it has yet to be tested against such a device.
One US official said the North Korean launch added urgency to longstanding informal discussions about a possible THAAD deployment to South Korea.
"Speed is the priority," said the official, who asked not to be named ahead of a formal decision.