US Secretary of State Mike Pompeo arrived in Pyongyang to prepare for historic talks between North Korean leader Kim Jong-Un and President Donald Trump.
Mr Pompeo said he hoped to finalise plans for talks on the denuclearisation of the Korean peninsula.
The surprise visit came amid growing speculation over the possible release of three US detainees.
It is his second trip to Pyongyang after meeting with Mr Kim last month.
Mr Pompeo said that a "good relationship" was formed at the meeting in April, which marked the highest level US contact with North Korea since 2000.
Ahead of his latest visit to Pyongyang, Mr Pompeo said he hoped North Korea would "do the right thing" and release three Americans imprisoned in the country.
"We’ve been asking for the release of these detainees for 17 months," he said.
A South Korean presidential official told news agency Yonhap that Pyongyang is expected to release the US citizens as a "goodwill gesture" ahead of the summit between Mr Kim and Mr Trump.
A State Department official travelling with Mr Pompeo said the US would also be "listening for signs from North Korea that things have substantially changed" with the nation’s nuclear ambitions.
Mr Trump also referred to Mr Pompeo’s latest visit while announcing that the US was withdrawing from an Obama-era nuclear agreement with Iran.
Nsanzimana Ernest ni Umwanditsi mukuru w’Ikinyamakuru Umuryango. Yatangiye gukorera iki kinyamakuru muri Nzeli 2016, afite Impamyabumenyi y’Icyiciro cya Kabiri cya Kaminuza (A0) mu Itangazamakuru n’Itumanaho yakuye muri Kaminuza y’u Rwanda Ishuri ry’ itangazamakuru n’ itumanaho