(CNN) — Secretary of State Mike Pompeo called on members of the United Nations to enforce sanctions against North Korea more strictly and for North Korean leader Kim Jong Un to keep his promise to denuclearize.

While Pompeo spoke generally about the need for countries to keep their pledge to enforce sanctions, the US ambassador to the UN, Nikki Haley, directly called out Russia and China for blocking US attempts to increase the pressure on Pyongyang.

Pompeo, speaking to reporters at the UN with Haley at his side, said he and President Donald Trump remain “upbeat” about the prospects of reaching a denuclearization agreement with Kim, even as he seemed to betray some frustration when asked what he needs to see from North Korea.

“It’s really pretty straightforward, right,” Pompeo said. “And it’s not my — it’s not my description of what needs to take place. Chairman Kim made a promise. Chairman Kim told not only President Trump, but (South Korean) President Moon that he was prepared to denuclearize. The scope and scale of that is agreed to. The North Koreans understand what that means. There’s no mistake about what the scope of denuclearization looks like.”

‘It’s the truth’

“So what do we need to see?” Pompeo asked. “We need to see Chairman Kim do what he promised the world he would do. It’s not very fancy, but it’s the truth.”

Earlier, Pompeo had said he and Trump are optimistic that progress is taking place. “President Trump remains upbeat about the prospects of denuclearization of North Korea,” the top US diplomat said. “So do I, as progress is happening.”

But Pompeo was at the UN with Haley to address problems, not progress. He noted that Pyongyang had illegally smuggled oil 89 times in the first five months of the year using ship-to-ship transfers.

North Korea is currently smuggling petroleum products “into the country at a level that far exceeds the quotas established by the United Nations,” Pompeo said, adding that “illegal ship-to-ship transfers are the most prominent means by which this is happening.”

These transfers continue to occur, he said. “The United States reminds every UN member state of its responsibility to stop illegal ship-to-ship transfers, and we urge them to step up their enforcement efforts as well,” Pompeo said. When sanctions are not enforced strictly, “the prospects for the successful denuclearization are diminished.”

‘What are they telling us?’

Haley called out Russia and China directly. She referred to a US attempt Thursday to bring a complaint before the UN to discipline North Korea for its smuggling. China and Russia blocked the measure.

“We have photographs of proof of ship-to-ship transfers,” Haley said. Speaking of the US complaint, she added, “Now for China and Russia to block it, what are they telling us? Are they telling us that they want to continue supplying this oil? They claim they need more information. We don’t need any more information. The sanctions committee has what it needs. We all know it’s going forward.”

Pompeo also called on UN members to crack down on other forms of sanctions evasion, “including the smuggling of coal by sea, smuggling by overland borders and the presence of North Korean guest workers in certain countries.”

The secretary said North Korean cyber thefts and other criminal activities are also generating significant revenue for the regime, “and they must be stopped.”

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