Sung Kim, the US special representative on North Korea, met in Washington with his South Korean counterpart, Noh Kyu-duk, ahead of a three-way meeting Tuesday with senior Japanese official Takehiro Funakoshi.

"We will seek diplomacy with the DPRK to make tangible progress that increases the security of the United States and our allies," Kim said, referring to the North by its official name, the Democratic People's Republic of Korea.

"We harbor no hostile intent toward the DPRK and we are hopeful to meeting with them without conditions," Kim told reporters.

But he added that the allies had "a responsiblity to implement UN Security Council resolutions," referring to sanctions which North Korea seeks to see lifted.

North Korean leader Kim Jong Un last week blamed the United States for sanctions, dismissing Washington's assertions that it does not have hostile intentions.

North Korea in recent weeks has tested a long-range cruise missile, a train-launched weapon and what it said was a hypersonic warhead.

Kim met three times with former president Donald Trump, who boasted of stopping a war but failed to reach a comprehensive agreement on ending North Korea's nuclear program.

President Joe Biden has promised to keep seeking diplomacy but with a more low-key approach looking for areas for progress.