NORTH Korea is continuing to produce fissile material for nuclear bombs despite its pledge to denuclearise.

Asked at a Senate foreign relations committee hearing whether this was the case, US Secretary of State Mike Pompeo responded to Democratic Senator Ed Markey by saying: “Yes, that’s correct. Yes, they continue to produce fissile material.”

Pompeo declined to respond when asked whether North Korea was continuing to pursue submarine-launched ballistic missiles or whether its nuclear program was advancing generally.

He said he would be happy to answer the latter question if necessary in a classified setting but suggested public statements on the issue would not help “a complex negotiation with a difficult adversary”.

Pompeo defended what he termed progress in talks with North Korea stemming from an unprecedented June 12 summit between President Donald Trump and North Korean leader Kim Jong-un in sometimes testy exchanges with sceptical politicians.

He said the United States was engaged in “patient diplomacy” to persuade North Korea to give up its nuclear weapons, but would not let the process “drag out to no end.”

Briefing on his July 5-7 visit to North Korea, Pompeo said he had emphasised this position in “productive” discussions with his North Korean interlocutor, Kim Yong-chol.

He said Trump remained upbeat about the prospects for North Korean denuclearisation, but Kim needed to follow through on his summit commitments.

Pompeo said US North Korea policy was guided by a principle stated by Trump on July 17 that “diplomacy and engagement are preferable to conflict and hostility”.

Trump has hailed his summit with Kim as a success, but questions have been growing about North Korea’s willingness to give up a nuclear weapons program that threatens the United States.

Kim committed in a summit statement to work towards denuclearisation but Pyongyang has offered no details as to how it might go about this.

Pompeo said a great deal of work remains ahead of a North Korea denuclearization deal, but he dodged requests to identify a specific denuclearization timeline in testimony to members of the Senate Foreign Relations Committee.

“There is an awful long way to go” Pompeo told lawmakers.

After Pompeo’s trip to the North Korean capital earlier this month, Kim accused the envoy of making “gangster- like” demands.

Lawmakers pressed the top US diplomat on whether the US and North Korea reached a denuclearisation agreement.

Pompeo responded that North Korea’s leadership “indicated that they fully understand the scope of what denuclearisation entails.”

When asked to detail verifiable evidence of progress toward denuclearisation, Pompeo stated: “We are sitting at the table having conversations.”

Pompeo also pointed to a report this week from an American research group that the North has begun dismantling its main missile-engine test site.

The report was based on an analysis of satellite imagery by the website 38 North.

Following the Singapore summit, Trump declared Pyongyang was already returning long-sought remains of Americans killed during the Korean War, which was not accurate.

He later modified his comments on the matter, saying North Korea had “already sent back or are in the process of sending back” remains.

Pompeo said the remains would be returned “in relatively short order.”