The US admiral expected to become the country's next ambassador to South Korea says North Korea remains the most imminent threat to peace in the Pacific but China's "dream of hegemony" is Washington's biggest long-term challenge.

There are few notable personalities on the northern side of the Korean peninsula's demilitarized zone. But one of them, Kim Yong Chul, has been dispatched to the US, in the latest signal from Pyongyang that Kim Jong Un is serious about pursuing talks with US President Donald Trump.

One of North Korean leader Kim Jong Un's top officials is believed to be traveling to the United States as the two countries lay the groundwork for on-again, off-again talks between Kim and US President Donald Trump in Singapore on June 12.