US says no softening in stance as envoy heads to North Korea

The State Department is pushing back against suggestions the Trump administration has softened its stance on North Korea as the top US diplomat travels to Pyongyang for crucial nuclear talks.

Department spokeswoman Heather Nauert tells journalists accompanying Secretary of State Mike Pompeo that US policy hasn't changed. She says the US remains "committed to a denuclearised North Korea."

Pompeo will press North Korea to take concrete action to back up its commitment to "complete denuclearisation" of the Korean Peninsula made at the June summit between President Donald Trump and the North's Kim Jong-un.

Despite reports that North Korea is continuing its nuclear program, Trump has remained upbeat, tweeting this week that conversations with North Korea were "going well!"

"Many good conversations with North Korea-it is going well!" he tweeted. "In the meantime, no Rocket Launches or Nuclear Testing in 8 months. 

"All of Asia is thrilled. Only the Opposition Party, which includes the Fake News, is complaining. If not for me, we would now be at War with North Korea!"

There have been reports Kim's regime has failed to honor its denuclearisation pledge after the June 12 meeting.

The Washington Post on Sunday quoted unnamed US officials who were briefed on intelligence findings that point to preparations for deceiving the United States, while NBC news has said Pyongyang is increasing its nuclear fuel production.

Citing satellite imagery, a monitoring group last month said operations and infrastructure works were continuing at the North's main Yongbyon nuclear site, while the Trump administration itself has cited "an unusual and extraordinary threat" from Pyongyang's nuclear arsenal to extend decade-long sanctions.

A report in Axios on Monday suggested if talks go well, Trump could invite Kim to New York in September to continue the dialogue as the UN General Assembly gets under way.

Separately, the US State Department confirmed that Secretary of State Mike Pompeo had spoken by telephone to his Russian counterpart Foreign Minister Sergei Lavrov.

Pompeo is due in North Korea for talks on a nuclear deal later this week, and his spokeswoman Heather Nauert said the issue came up in his conversation with Lavrov, along with the war in Syria and preparations for Trump's summit with Russia's President Vladimir Putin.