United States Secretary of State Michael Pompeo on Tuesday abruptly postponed a meeting with a top North Korean official in New York scheduled for Thursday, in a setback to peace talks between the two countries, AFP reported.

Department of State spokesperson Heather Nauert said the talks between Pompeo and the North Korean delegation “will now take place at a later date” without giving a reason. “We will reconvene when our respective schedules permit,” she said in a statement.

Nauert said the US remained focussed on fulfilling the commitments agreed to by President Donald Trump and North Korean leader Kim Jong-un at the Singapore summit in June, reported The Washington Post.

The State Department had earlier confirmed that Pompeo would meet Kim Yong Chol, a close aide of Kim, in New York to discuss progress toward a denuclearisation pact and to arrange a second summit following the historic talks between Trump and Kim in June.

South Korea, however, said the delay does not mean the summit won’t happen or “momentum for the summit has been lost”, reported Reuters, quoting presidential spokesperson Kim Eui-kyeo.

The cancellation of the talks comes just a week after North Korea threatened to resume its nuclear weapons programme if the US failed to lift sanctions against the country. North Korea’s Foreign Ministry said the US President Donald Trump’s administration had failed to understand its repeated demand.

The development comes amid strained ties between South Korea and the US over how to negotiate denuclearisation with North Korea. Seoul is of the view that Pyongyang can be encouraged towards nuclear disarmament through economic development, while Washington has set a complete shutdown of its nuclear weapons programme as a prerequisite for the lifting of sanctions.

On Sunday, Pompeo said he was “not worried” about the North Korean demands and insisted there would be “no economic relief until we have achieved our ultimate objective.” Pompeo has travelled four times this year to North Korea to work on achieving an accord.