Beijing suggested following Tuesday's historic summit between US President Donald Trump and North Korean leader Kim Jong Un that the UN Security Council could consider easing sanctions if Pyongyang fulfilled its obligations.

Speaking to reporters after talks with Foreign Minister Wang Yi in Beijing, Pompeo said "China has reaffirmed its commitment to honouring the UN Security Council resolutions."

The resolutions "have mechanisms for relief contained in them and we agreed that at the appropriate time that those would be considered," Pompeo said.

But, he added, "we have made very clear that the sanctions and the economic relief that North Korea will receive will only happen after the full denuclearisation, the complete denuclearisation of North Korea."

Beijing is Pyongyang's sole major ally and main trading partner, but it has backed the UN sanctions.

Despite tensions, the Cold War-era allies have sought to mend ties recently, and Kim borrowed an Air China plane to travel to the landmark summit in Singapore.

For his part, Wang said China has a "firm commitment" to denuclearisation but that North Korea's "legitimate" concerns must be addressed.

Wang said the denuclearisation process would be worked out "through more detailed and specific consultations going forward" and "China stands ready to play a constructive role in that process".