The United States on Monday brushed aside North Korea's threat to take "physical counter-action" against the planned deployment of the U.S. THAAD missile defense system in South Korea, saying such a threat only confirms the deployment decision was right.

The North's military issued the threat earlier Monday, claiming that the agreement between the South and the U.S. to deploy a Terminal High Altitude Area Defense battery in the South is part of their efforts to invade the communist nation.

The U.S. Defense Department rejected the threat.

"We came to this alliance decision because of North Korea's continued belligerence and its ongoing pursuit of ballistic missile and WMD capabilities despite multiple condemnations by the international community," Cmdr. Gary Ross, a Pentagon spokesman, told Yonhap News Agency.

"Incidents like this only confirm the prudence of our alliance decision, and we will continue to ensure that our defense posture remains capable of deterring conflict and defending ourselves and our allies," he said.

In an apparent protest the THAAD deployment decision, the North also test-launched a submarine-launched ballistic missile on Saturday, but the test ended in failure with the missile exploding at an altitude of some 10 kilometers after being launched from a submarine.

The U.S. had long desired to deploy THAAD to 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. (Yonhap)