Rex Tillerson has said that the US is ready to begin exploratory talks with North Korea “without preconditions”, but only after a “period of quiet” without new nuclear or missile tests.

The secretary of state’s remarks appeared to mark a shift in state department policy, which had previously required Pyongyang to show it was “serious” about giving up its nuclear arsenal before contacts could start. And the language was a long way from repeated comments by Donald Trump that such contacts are a “waste of time”.

Tillerson also revealed that the US had been talking to China about what each country would do in the event of a conflict or regime collapse in North Korea, saying that the Trump administration had given Beijing assurances that US troops would pull back to the 38th parallel that divides North and South Korea, and that the only US concern would be to secure the regime’s nuclear weapons.