Relations between Pyongyang and Seoul are at one of their lowest points ever, with diplomacy stalled and North Korean leader Kim Jong Un calling for increased weapons development, including tactical nukes.

In response, President Yoon Suk Yeol has pulled South Korea closer to long-standing ally Washington, and even sought to bury the hatchet with former colonial power Japan in a bid to contain North Korea.

In April, Seoul and Washington said that if Pyongyang ever used its nuclear weapons against the allies, it would face a nuclear reaction and the "end" of its regime.

"The Korea-US-Japan trilateral summit is scheduled to be held in the United States in August," Seoul's presidential office said Thursday, adding the specific date and location would be "announced later".

The Yonhap News Agency reported the meeting will take place on August 18 at Camp David near Washington, citing unnamed sources.

The announcement comes days after Seoul and Washington held their first Nuclear Consultative Group meeting in the South Korean capital.

On Tuesday, a nuclear-armed American submarine made a port visit to Busan for the first time since 1981.

Pyongyang last week said it had successfully tested the Hwasong-18, its new solid-fuel intercontinental ballistic missile, for the second time.

Analysts say the tests represent a major breakthrough for North Korea's banned weapons programmes.

The announcement also comes as Washington confirmed Tuesday that a US soldier -- who had been jailed in the South on assault charges -- is believed to have been detained by North Korea after crossing the border.

Pyongyang has a long history of detaining Americans and using them as bargaining chips.