North Korea on Saturday said that high-level talks with a United States delegation led by Secretary of State Mike Pompeo were regrettable and accused Washington of trying to unilaterally pressure the country into abandoning its nuclear programme, reported AP.

“The US attitude and positions at the high-level talks on Friday and Saturday were extremely regrettable,” North Korea’s foreign ministry said, AFP reported quoting Yonhap news agency.

The statement came just hours after Pompeo said that talks with his North Korean counterpart on how to dismantle the Pyongyang’s nuclear programme have been “very productive”, AFP reported.

Pompeo met North Korean senior official Kim Yong Chol, who played a key role in arranging last month’s summit between US President Donald Trump and North Korean leader Kim Jong Un in Singapore.

“These are complicated issues but we made progress on almost all of the central issues,” he told reporters, according to Reuters. “Some places a great deal of progress, other places there’s still more work to be done.”

He said the two sides spent good time discussing denuclearisation timeline and the North’s nuclear and missile facilities. He also discussed the repatriation of the remains of US soldiers missing from the 1950-’53 Korean War.

A state department spokesperson said Pompeo had been very firm in focusing on denuclearisation, and other security assurances, BBC reported. US State Department spokesperson Heather Nauert said Pompeo did not meet Kim Jong-un during his visit, but he handed over a letter to the North Korean leader from Trump.

However, the North said the outcome of the talks was “very concerning” as it had led to a dangerous phase which might rattle the country’s “willingness for denuclearisation that had been firm”. Pyongyang said the US had betrayed the spirit of the summit by making “one-sided and robber-like” demands on the denuclearisation of North Korea.

Kim Jong-un had promised to work towards denuclearising the Korean peninsula during his meeting with Trump on June 12. They had also agreed to establish formal diplomatic relations.

A few weeks later, however, Trump renewed sanctions against North Korea for a year, claiming that the country still posed an “extraordinary threat”. The move came despite Trump claiming during the summit that North Korea was “already destroying a major missile site”.

A website monitoring Pyongyang released a report in late June suggesting that North Korea was continuing to carry out rapid improvements to its nuclear research facility.