North Korean leader Kim Jong Un may travel to Russia to meet President Vladimir Putin for discussions on a potential deal to supply Moscow with weapons for its war on Ukraine, according to the US government. The National Security Council warned Monday that arms negotiations between Russia and North Korea are “actively advancing,” after Russian Defense Minister Sergei Shoigu visited Pyongyang in July in an attempt to convince it to sell artillery ammunition to Moscow. “We have information that Kim Jong Un expects these discussions to continue, to include leader-level diplomatic engagement in Russia,” the council’s spokesperson, Adrienne Watson, said in a statement. Watson did not say when and where a potential meeting between Kim and Putin in Russia might take place. But South Korea’s National Intelligence Service said Tuesday it is “closely monitoring… the possibility of Kim Jong Un visiting Russia soon.” CNN has asked the Russian embassy in Washington for comment. The Kremlin declined to comment on the claim. “We have nothing to say on the subject,” Kremlin spokesman Dmitry Peskov told journalists during a call on Tuesday. US national security adviser Jake Sullivan told reporters at a White House briefing Tuesday that discussions between North Korea and Russia are “actively advancing,” and is evidence that economic sanctions against Russia have succeeded in shrinking the country’s defense industrial base. “We will continue to call it out, and we will continue to call on North Korea to abide by its public commitments not to supply weapons to Russia that will end up killing Ukrainians – over time, we have not seen them actively supply large amounts of munitions or other military capacity to Russia for the war in Ukraine,” Sullivan said. “I cannot predict you what will happen at the end of this, I can only say that the discussions have been actively advancing and the Russians have imbued them with an increased intensity – as reflected in the fact that their Defense Minister, their number one guy in their defense establishment, actually got on a plane and flew to Pyongyang to try to push this forward,” he said, adding that it’s possible, in the near future, that those discussions may see North Korea’s Kim Jong Un participate in “leader level discussions, perhaps even in-person leader level discussions.” As discussions advance, the US and its allies are concerned about the technology North Korea is seeking from Russia in return for weaponry, according to two US officials. North Korea is seeking technology that could advance their satellite and nuclear-powered submarine capabilities, officials said, which could significantly advance North Korea’s capabilities in areas that the rogue regime has not fully developed. Just last month, North Korea’s second attempt to launch a spy satellite into orbit failed, a report from the state-run Korean Central News Agency said. North Korea does not currently have any nuclear-powered submarines, according to an assessment from Nuclear Threat Initiative, a think-tank focused on reducing nuclear threats. The New York Times first reported the potential meeting between Kim and Putin in Russia, saying it is expected to take place this month. According to the report, the meeting may take place on the campus of a university in the eastern port city of Vladivostok, where the Eastern Economic Forum is scheduled to be held from September 10 and 13. In 2019, Kim made his first trip to Russia as the leader of North Korea and traveled from Pyongyang to Vladivostok on an armored green train. Going by train is the preferred mode of travel by the reclusive North Korean leader. Kim’s possible visit to Russia comes as the US has expressed increasing concerns about North Korea’s military assistance to Russia’s war effort in Ukraine – a move that would be in breach of US sanctions. Earlier this month, the US Treasury imposed sanctions on three entities it accused of being tied to arms deals between North Korea and Russia. Since Shoigu’s July visit, a second delegation of Russian officials have visited Pyongyang for further discussions on a potential deal, while Putin and Kim have exchanged letters “pledging to increase their bilateral cooperation,” National Security Council spokesman John Kirby told reporters last week. North Korea delivered infantry rockets and missiles into Russia for use by Wagner forces late last year, and the potential deal being discussed would provide Russian troops with much more weapons, according to Kirby. “Under these potential deals Russia would receive significant quantities and multiple types of munitions form the DPRK, which the Russian military plans to use in Ukraine,” he said. “These potential deals could also include the provision of raw materials that would assist Russia’s defense industrial base,” Kirby added, pledging that the US would take direct action to sanction any entities involved in a potential deal and urging Pyongyang to cease the negotiations. The Biden administration has routinely declassified intelligence about the support Russia is receiving – or is planning to receive – in an effort to deter countries from providing support for Moscow’s war effort. Apart from North Korea, Russia has also received drones and artillery from Iran. Chinese state-owned defense companies have sent technology and equipment to Russia, but US officials say they have seen no signs so far that China has provided weapons or lethal military aid to Russia. On Monday, Shoigu, the Russian Defense Minister, said Russia was also discussing holding joint military exercises with North Korea. “We are discussing it with everyone, including the Democratic People’s Republic of Korea. Why not? These are our neighbors,” Shoigu told reporters, referring to North Korea by its official name. “You don’t choose your neighbors, and it’s better to live in peace and harmony with your neighbors,” he said, citing an old Russian saying. Russia has been holding the annual Eastern Economic Forum in Vladivostok since 2015 in an attempt to encourage foreign investment in the Russian Far East. China, Russia’s closest diplomatic partner, has often sent high-level delegations to the event. Chinese leader Xi Jinping attended the forum in-person in 2018, while top legislator Li Zhanshu, the third-ranking leader of the ruling Communist Party, attended last year. Beijing has not announced which official will lead its delegation this year. The forum will partially overlap with the Group of 20 leader’s summit in India. China’s has indicated that Xi will skip that summit for the first time since he came to power.