The United States hopes to deploy its Terminal High Altitude Area Defense or THAAD system to the Korean peninsula as soon as possible.
"We'd like to see this move as quickly as possible. We are beginning the consultations now in the coming days with the South Koreans and we expect this will move in an expeditious fashion."
The official's remarks come after South Korea and the United States agreed to discuss the matter on Sunday, the same day North Korea launched its long-range rocket.
Citing a U.S. official, CNN reported that Washington wanted to deploy THAAD as early as next week, adding to speculation the system could be on South Korean soil soon.
On Monday, U.S. President Barack Obama said for the first time that Washington and Seoul were in talks over boosting missile defense capabilities to prevent any possibility that North Korea could hit U.S. facilities or populations.
The White House reaffirmed the THAAD system is intended to protect South Korea.
"As a result of this launch the United States has begun formal consultations with our allies in South Korea about, about moving equipment and technology that could support a THAAD system into South Korea to protect our allies there."
The White House added THAAD would only be used to counter threats from Pyongyang -- a statement echoed by the Pentagon.
"If the THAAD system were to be deployed to the Korean Peninsula, it would be focused solely on North Korea and contribute to a layered missile defense."
China is deeply opposed to the deployment, as THAAD's radar has a radius of some two-thousand kilometers, meaning it could cover half of mainland China when deployed in Pyeongtaek, one of the candidate locations for the THAAD system.
China's foreign ministry says the deployment of such a powerful piece of military hardware to the peninsula would detract from efforts to maintain peace and security in the region.
Connie Kim, Arirang News.