The United States remains in contact with Chinese and Russian leaders "at the highest levels,"

the Pentagon said Friday, as Beijing and Moscow protest strongly the planned deployment of the U.S. THAAD missile defense system to South Korea.

South Korea and the U.S. announced earlier that they have officially decided to deploy a Terminal High Altitude Area Defense battery to South Korea to cope with ever-growing nuclear and missile threats from North Korea.

China, which has long voiced opposition to THAAD in the South, strongly protested the decision, saying the deployment does not help achieve the denuclearization of the Korean Peninsula and hurts peace and stability in the region.

Russia also expressed similar protests.

"As we have long said, THAAD is a purely defensive system designed to counter short- and medium-range regional ballistic missiles. It would not undermine China's or Russia's strategic deterrent," Cmdr. Gary Ross, a Pentagon spokesman, told Yonhap News Agency.

"A THAAD system in the ROK (South Korea) would be focused solely on North Korea and contribute to a layered missile defense that would enhance the alliance's existing missile defense capabilities against potential North Korean missile threats," he said.

Asked if Secretary Ash Carter or other senior Pentagon officials have any plans to hold talks with Chinese or Russian officials about THAAD, Ross said, "We also remain in contact with Chinese and Russian leaders at the highest levels."

China has long claimed that THAAD, especially the powerful X-band radar that comes with the system, can be used against it, despite repeated assurances from Washington that the system is aimed only at deterring North Korean threats.

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.

State Department spokesman John Kirby said there is no reason China should be concerned.

"We continue to need, as the secretary said yesterday, continue to need Chinese leadership and Chinese influence in a productive way with respect to North Korea. There's no reason why this deployment should be of concern to Chinese leaders since it is a purely defensive measure and because the North continues to pose such a real and significant threat to South Korea," Kirby said.

He also said the U.S. is ready to brief Chinese officials on the way THAAD works.

"We have certainly listened to their concerns and we have offered to provide informational briefings for them on the way the system works. Again, this is a purely defensive system that we wouldn't have to talk about, wouldn't have to consider if the DPRK had proven in recent weeks and months willing to take a different, more peaceful path," he said. (Yonhap)