A South Korean opposition party on Thursday called on the government to ensure the United States won't settle for North Korea's nuclear freeze rather than complete denuclearization.

US Secretary of State Rex Tillerson said Tuesday North Koreans have "too much" invested in its nuclear program, while President Donald Trump is "very realistic" about it. Tillerson also said Washington is ready to talk with Pyongyang without preconditions.

"We have to mobilize all of our diplomatic capabilities to ensure that the United States will not reach a compromise in a way that we do not want," Yoo Seong-min, the leader of the minor Bareun Party, said during a meeting with senior party officials.

"If the US attempts to clinch a compromise that would help block North Korea's intercontinental ballistic missiles and accept a nuclear freeze, that is not an outcome we want, though the US may like it," he added.

As the wayward state has been pushing to develop a nuclear-tipped long-range missile capable of striking the continental US, speculation emerged that Washington may seek a compromise with the North to ease military tensions.