South Korea's chief nuclear envoy met with his U.S. counterpart Monday for talks expected to focus on discussing how to restart long-stalled negotiations aimed at ending North Korea's nuclear programs.

Hwang Joon-kook, Seoul's special representative for Korean Peninsula peace and security affairs, arrived in Washington earlier in the day for talks with Amb. Sung Kim, special representative for North Korea policy, and other U.S. officials.

Details of Hwang's discussions with Kim were not immediately available, but a State Department spokesperson said they had "a very productive discussion on a wide range of issues related to the Democratic People's Republic of Korea."

"The United States and the ROK agree on the fundamental importance of a denuclearized North Korea. Special Representative Hwang's visit reflects the close cooperation between our countries and our continued focus on pursuing the verifiable denuclearization of North Korea in a peaceful manner," the official said.

Hwang's trip, which will take him to Beijing later this week, came after North Korean leader Kim Jong-un called off a planned visit to Russia and suggested the regime could conduct yet another long-range rocket launch in the name of launching a satellite.

Upon arrival in Washington, Hwang said the current situation is "fluid."

"We will exchange assessments of the situation with each other and discuss the direction of our response. In particular, we will focus our discussions on how to move forward 'exploratory talks' and denuclearization talks," Hwang told reporters at the airport.

The term "exploratory talks" refers to a compromise form of negotiations aimed at meeting both Pyongyang's demand for unconditional resumption of talks and U.S. insistence that any formal negotiations should begin only after Pyongyang takes concrete steps demonstrating its denuclearization commitment.

Five dialogue partners with North Korea -- South Korea, China, Japan, Russia and the U.S. -- have reportedly reached a consensus on holding exploratory talks with Pyongyang, but the communist nation has not shown any interest.

In Washington, Hwang also plans to meet with Daniel Glaser, the Treasury's assistant secretary for terrorist financing, to discuss sanctions imposed on North Korea.

On Wednesday, he will meet with his Chinese counterpart, Wu Dawei, in Beijing before flying to London to deliver a speech at the Chatham House think tank on Friday about South Korea's diplomacy aimed at resolving the North Korean nuclear issue.

The six-party talks have been stalled since late 2008. Since then, the North has bolstered its nuclear capabilities and stockpile and conducted its second and third nuclear tests, in 2009 and 2013. Some experts now warn that the communist nation's nuclear arsenal could expand to 100 bombs by 2020. (Yonhap)