The US believes North Korea has advanced its missile capabilities with the latest launch of a long-range rocket on Sunday and wants to fortify allies' defence systems to forestall any threat from Pyongyang.
Before the meeting of top military commanders in Hawaii next week, high level US and South Korean officials started formal talks on deploying a highly advanced missile defense system to South Korea as soon as possible.
The advanced missile defence system can be in place in South Korea within two weeks of the deployment order, AFP quoted officials as saying.
"Without getting into a timeline, we'd like to see this move as quickly as possible," a Pentagon spokesman told the agency.
This means South Korea will get the sophisticated Terminal High Altitude Area Defense (THAD) system built by Lockheed Martin Corp along with the associated AN/TPY-2 tracking radar built by Raytheon.
North Korea said it put a satellite into orbit at Sunday's rocket launch, but the US, South Korea and Japan beehive it was part of a secretive programme to develop a missile system that can carry nuclear warheads in future.
"This launch, coupled with the recent nuclear test, indicates further advances in the technology necessary to improving North Korea's capability to strike the continental United States, Alaska or Hawaii ... Now the threat is more serious," Ken Todorov, a former deputy director of the US Missile Defense Agency, told Reuters.
However, the deployment of THAAD missile to South Korea will likely increase tension between China and the US. The sophisticated system can fire anti-ballistic missiles targeting objects inside or outside the Earth's atmosphere.
Meanwhile, President Barack Obama said on Monday he was not surprised by Pyongyang's rocket launch.
"This is an authoritarian regime. It's provocative. It has repeatedly violated UN resolutions, tested and produced nuclear weapons and now they are trying to perfect their missile launch system," Oabama said.