WASHINGTON -- The United States and the Republic of Korea(ROK) have begun negotiations on the deployment of a missile defense system in response to the missile launch by the Democratic People's Republic of Korea (DPRK), the Pentagon said Monday.

"The goal of the formal consultations is to bilaterally explore the feasibility of THAAD (Terminal High Altitude Area Defense) deploying to and operating on the Korean Peninsula at the earliest possible date," Peter Cook, spokesman for the Department of Defense, said at a press briefing.

Cook stressed that the negotiations underscore the "ironclad" commitment of the United States to defend South Korea.

On Sunday, South Korea's defense ministry said the country and the United States had agreed to launch an official negotiation on the deployment of THAAD on the Korean peninsula in response to nuclear test and missile launch by the DPRK.

The DPRK said Sunday that it had successfully launched a Kwangmyongsong-4 Earth observation satellite into orbit less than 10 minutes after liftoff at 9:30 a.m. (0030 GMT), about a month after Pyongyang claimed it had successfully its first hydrogen bomb.

China has expressed deep concerns over the decision by the U.S. and South Korea to launch an official negotiation on the deployment of THAAD.

"China holds a consistent and clear stance on the anti-missile issue," Chinese Foreign Ministry spokesperson Hua Chunying said Sunday. "When pursuing its own security, one country should not impair others' security interests."

At the Pentagon, Cook said the THAAD system would be "focused solely" on the DPRK.