SEOUL (REUTERS) - US Secretary of State Mike Pompeo is "very firm" on complete denuclearisation of North Korea as he began a second day of talks in Pyongyang on Saturday (July 7), according to a pool report from reporters travelling with him.

State Department spokesman Heather Nauert said there has been no softening in Washington' position towards the North's denuclearisation.

She said Mr Pompeo is being "very firm" in seeking three basic goals - complete denuclearisation of North Korea, security assurances, and the repatriation of the remains of US service members from the 1950-53 Korean War, according to the report.

Earlier Ms Nauert said US and North Korean officials have set up working groups to deal with "nitty gritty stuff" including verification of efforts to achieve denuclearisation.

She said Mr Pompeo's discussions with North Korean officials included the repatriation of the remains of Americans who died in the Korean War in the 1950s in addition to denuclearisation issues, according to a pool report by reporters accompanying Pompeo.

Mr Pompeo left the negotiations venue to make a secure phone call to update President Donald Trump on the talks, the report said.

At talks with Mr Kim Yong Chol, a top official in North Korea's ruling party who had already met with Mr Pompeo in New York, Mr Pompeo said as he headed into the meeting that the aim of the US was for "complete denuclearization" of the North.

Mr Kim did not comment on the issue of denuclearisation, saying only that there "are things I have to clarify". The Trump administration has said that if North Korea abandons its nuclear weapons programme it could become a rich and successful country.

While there have been no nuclear or missile tests since the Singapore summit between Mr Trump and North Korean leader Kim Jong Un last month, satellite imagery shows upgrades to the country's Yongbyon nuclear plant.