Chung Eui-yong, left, head of the National Security Office, speaks to reporters at Incheon International Airport, Thursday. / Yonhap

South Korean President Moon Jae-in's top security adviser left Thursday for the United States to explain the outcome of his recent trip to North Korea that led to what many here have called "exceptional" concessions from the communist state, such as plans for an inter-Korean summit.

Chung Eui-yong, head of the National Security Office, has quoted North Korean leader Kim Jong-un as saying the North is willing to suspend all its military provocations, including ballistic missile tests, as long as U.S.-North Korea dialogue was in progress.

He will directly explain the outcome of his Pyongyang trip to the highest U.S. officials during his three-day visit to Washington, an official from the presidential office Cheong Wa Dae told reporters.

The U.S. officials he will meet with are widely expected to include National Security Advisor Herbert McMaster and State Secretary Rex Tillerson.

Both Washington and Pyongyang have expressed their willingness to talk, but the U.S. is still seen to be skeptical about the North's intentions.

Following the two-day trip by Moon's special envoys to North Korea, U.S. President Donald Trump said the North appeared to be "sincere."

In an unprecedented meeting with the South Korean officials, Kim also said his country was willing to denuclearize in exchange for a security guarantee.

Chung earlier said he carried additional messages for the U.S. from North Korea.

Moon's special envoys included Suh Hoon, the chief of South Korea's spy agency, the National Intelligence Service. He, too, headed to Washington on Thursday, according to the Cheong Wa Dae official.

Chung and Suh will later visit China, Japan and Russia to inform them of the outcome of their North Korea trip.

The three countries, along with the U.S., are involved in the six-nation talks aimed at ridding North Korea of nuclear weapons. The talks, also attended by the two Koreas, have stalled since late 2008. (Yonhap)