"We think it has to be conditions-based because of the seriousness of the security environment there and the need to ensure that we're as capable and prepared as possible," Schriver said. "So when we look at things like command structure, when we look at things like certain key capabilities for that contingency, we're going to be pretty insistent that South Korea acquires those capabilities before we agree to the transfer and not be tied to any political calendar."

He warned, however, that the frictions between South Korea and Japan will only benefit countries such as China, Russia and North Korea.

"And that's not a good place to be," he said, adding that defense officials in Seoul, Washington and Tokyo continue to have regular interactions.

"We're trying our best to insulate the defense and security relationship from the political tensions that obviously are present," he said. "I think one of the reasons we spoke out on GSOMIA is because that was spilling into the security trilateral work in an unhelpful way, but overall I think we're doing okay."

Schriver added that he believes the prevailing security interests and security environment will ultimately bring the three countries back together, and that the US is open to finding ways to help its two allies resolve their differences.

The assistant secretary also called on China to tighten sanctions enforcement against North Korea ahead of the resumption of working-level denuclearization talks between Washington and Pyongyang this weekend.

"We believe China can do a little better on the sanctions enforcement and cooperating with us in an overall effort to get North Korea to the negotiating table in a constructive way," he said. "We've seen some slippage on sanctions enforcement, and we are willing to work with China to strengthen that enforcement effort." (Yonhap)