Defending against North Korea's new road-mobile intercontinental ballistic missiles is the main purpose of the United States' planned additional deployment of ground-based missile interceptors, a senior U.S. official has said.

Frank Rose, assistant secretary of state for arms control, verification and compliance, made the remark at an international missile defense conference in Barcelona on Friday, according to a transcript provided by the department.

"The Obama Administration has continued the efforts to defend the United States' homeland against potential limited intercontinental ballistic missile attacks from states like North Korea and Iran," Rose said.

"As part of this effort, in March 2013, the administration announced it would deploy an additional 14 ground-based interceptors, increasing the total number to 44 by 2017. This deployment will ensure that we stay ahead of the new road-mobile ICBM threat from North Korea," he said.

Rose was apparently referring to the North's KN-08 missile.

Even though the missile has not been tested yet, U.S. military officials have increasingly voiced concerns about the missile as it is harder to keep an eye on as it can be launched from mobile launchers.

In April, Adm. William Gortney, commander of the U.S. Northern Command, said the North is believed to be capable of miniaturizing nuclear warheads to put on its new KN-08 intercontinental ballistic missile and fire it at the U.S. mainland.

Rose also said that the U.S. is developing "a new radar that will provide persistent sensor coverage and improve discrimination capabilities against the North Korean threat" and is redesigning the kill vehicle for the ground-based interceptor.

Last month, the Pentagon unveiled a plan to deploy a long-range discrimination radar in Alaska by 2020, saying it will increase the capacity of the ground-based midcourse defense inventory of interceptors in Alaska and California.

"At the same time, we have made clear, both in our policy and in the capabilities we have deployed, that our homeland defense is not intended to affect the strategic balance with Russia and China," Rose said.

China and Russia have voiced strong opposition to the potential U.S. deployment of a Terminal High Altitude Area Defense missile defense battery in South Korea, claiming the deployment would hurt their security interests. (Yonhap)