The decision to place the THAAD missile defense system in South Korea was taken as part of U.S. obligations to defend the Asian ally from the "exceptionally irresponsible" leader Kim Jong-un of North Korea, the CIA chief was quoted as saying.

"Clearly Kim Jong-un continues to go down a road that is exceptionally irresponsible as far as regional and global security, with his development of nuclear weapons, as well as ballistic missiles," CIA Director John Brennan said at a Brookings Institution discussion last week, according to the Business Insider.

"He has demonstrated that he is not going to ratchet back on any of these activities," he said.

Earlier this month, South Korea and the United States announced they have officially decided to deploy a Terminal High Altitude Area Defense battery in the Asian nation to cope with the ever-growing nuclear and missile threats from North Korea.

"We have certain obligations to our partners and the region so that the appropriate steps are taken to reassure our friends, partners and allies of U.S. commitment to the security of that area," Brennan was quoted as saying.

"This is something that -- I think the president has demonstrated -- that we are trying to deal with these issues in a manner that is not going to lead to any escalation of tensions," he said. He also said that the process of deploying a THAAD battery is done in "very close consultation with our partners in the region."

The U.S. had long desired to deploy THAAD in the South, but Seoul had wavered over whether to accept the deployment because of strong objections from China that claimed the system, especially the powerful X-band radar that comes with it, could be used against it.

North Korea's fourth nuclear test in January and the long-range rocket launch the following month provided a strong impetus for the U.S. and South Korea to move ahead with formal discussions about the potential placement of THAAD in the South.

Pyongyang protested the decision to deploy THAAD, claiming it's part of a plot to invade the country and threatening to take "physical" counteractions against it. In an apparent protest against THAAD, the North also test-launched a submarine-launched ballistic missile. (Yonhap)