It was Yun's first meeting with the US' top diplomat under the Donald Trump administration, which came after North Korea's launch of an intermediate ballistic missile on Feb. 12. The provocation highlighted North Korea's nuclear issue as one of the most pressing security challenges facing the new US administration.

The sources said that the South Korean foreign minister stressed that a mere freeze on North Korea's nuclear program would be meaningless mainly because the country is believed to be already in possession of dozens of nuclear weapons and a freeze of North Korea's highly-enriched uranium program may be hardly verifiable.

"The (South Korean) government regards it as meaningless to pursue a freeze deal when North Korea shows no intention to give up its nuclear weapons program although freezing its nuclear facilities would be part of the inevitable process before the complete, verifiable and irreversible (nuclear) dismantlement," the sources told Yonhap News Agency.

During the meeting, Yun also expressed Seoul's skepticism about opening any dialogue over North Korea's demand to sign a peace treaty, the sources said. Pursuing talks with North Korea simultaneously on denuclearization and a peace treaty would give the regime an excuse to delay its denuclearization, Yun was also quoted as telling Tillerson.

The foreign minister then underlined the importance of maintaining the on-going pressure-oriented diplomacy toward North Korea, suggesting broader sanctions on North Korea and Chinese firms doing business with the North. He also called for continuing pressure on North Korea's human rights violations as a desirable policy approach toward the reclusive country, according to the sources.

Yun's policy stances are likely to be put to discussion when the South Korean and US representatives on the North Korean nuclear issue hold a meeting in Washington possibly before the end of this month.

Foreign ministry spokesman Cho June-hyuck said later, "The South Korean and U.S. foreign ministers shared in specific details in their first talks what our side thinks with regard to the two countries' joint response to North Korea's nuclear (development).

"In follow-up to the ministerial talks, special representative for Korean Peninsula peace and security affairs Kim Hong-kyun will travel to the US in the near future to put the puzzle together on the matters of joint response," he noted.

On the occasion of Kim's US trip, a separate three-way dialogue including Japan is also reportedly being planned. 

The spokesman said as of late, a total of 52 countries have joined in condemning North Korea's launch of an intermediate ballistic missile on Feb. 12, along with six international organizations. This marks three times the number of countries that condemned North Korea's ballistic missile launches in June and a test-fire of a submarine-launched ballistic missile in August, he added. (Yonhap)