The leaders of North Korea and Russia are scheduled to meet this week, with deepening military, economic and geopolitical cooperation on the official agenda.
Behind closed doors, however, White House officials and political analysts believe the talks between North Korean leader and Russian President will focus on arms deals and military cooperation that could potentially take their relationship to another, more disconcerting, level.
Ahead of Kim's arrival in Vladivostok, Russia, in the early hours of Tuesday morning, the Pentagon said it had no detail on where exactly, or when, Putin and Kim's meeting would take place.
"As far as the details of that meeting and what will be discussed and when and where, I just don't have any information to provide," Pentagon press secretary Brig. Gen. Pat Ryder said Monday.
"I would just again reiterate that we remain concerned that North Korea is contemplating providing any type of ammunition or materiel support to Russia, in support of their war against Ukraine."
There are concerns that Pyongyang could provide weaponry to Russia for use in its war in Ukraine, , anti-tank missiles and small arms ammunition. There are also fears about what Moscow might offer the economically isolated and heavily sanctioned North Korea in return.
The White House that any arms deal or military support for would directly violate a number of UN Security Council resolutions and added that it's ready to impose more sanctions against North Korea without hesitation.
Any deal between the two powers is expected to go beyond weaponry, with experts noting that this burgeoning "transactional" relationship could see advanced military technology and intelligence shared with Pyongyang — which could enable it to further that nuclear program and weapons of mass destruction.
North Korea has had numerous sanctions imposed on it due to its prohibited development and testing of missiles and nuclear weapons in recent years. That Russia could potentially share such information with a so-called rogue state like North Korea — and behave similarly itself as it threatens global peace and security — should worry the West, experts say.
"We should not be unconcerned" by this meeting, Edward Howell, lecturer in politics at Oxford University and an expert on North Korea's domestic and foreign policy, told CNBC.
"Pyongyang's rapprochement with Moscow could mean that a transactional network of information exchange — in addition to weapons and technological exchange — continues, including other rogue state actors, too," he said Monday.
"We must remember that in the past, North Korea has actively engaged in the clandestine proliferation of nuclear weapons-related technology and fissile material with Pakistan, Syria, and Libya."
Moreover, Howell said, such actions by Russia and North Korea would make it harder for international institutions to encourage re-compliance with the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) from which North Korea withdrew in 2003.
"If the UN Security Council becomes unable to dampen Pyongyang's nuclear ambitions, then the likelihood of North Korea getting away scot-free with a seventh nuclear test in the future becomes ever-higher," he added.
CNBC has contacted the Kremlin and North Korea's Embassy in London for comment and further details on the talks and is awaiting a reply.
For their part, Russia and have both denied claims of alleged arms dealing.
Kremlin press secretary Dmitry Peskov told reporters Tuesday morning that the talks would focus on "issues of bilateral cooperation," as well as "sensitive areas," without providing further detail.
Asked to comment on the White House's warning to North Korea about the potential sale of weapons to Russia, Peskov said Moscow and Pyongyang were not interested in statements from the U.S.
"The interests of our two countries are important for us, and not warnings from Washington. It is the interests of our two countries that we will focus on," he said, adding that Russia was also ready to discuss "issues related to the sanctions of the UN Security Council," without giving further details.
Kim's visit to Vladivostok, where the Eastern Economic Forum is taking place this week, is an unusual one . It's only his second visit to ally Russia and he is not believed to have left North Korea since .
Kim's trip to Vladivostok, which lies around 80 miles from the North Korean border, was made on his armored train, reported.
ahead of the meeting; North Korea and Moscow denied the claims.
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Western allies — and particularly Japan and South Korea that deal with North Korea's saber-rattling and unpredictability regularly, not to mention its nuclear and missile tests — say they're monitoring the Kim/Putin summit closely.
"We are watching the situation with concern, including the possibility that it could lead to a violation of the relevant UN Security Council resolutions that prohibit all procurement of weapons and related materials from North Korea, as well as the possible impact on Russia's aggression in Ukraine," Japan's government spokesman noted in a press briefing Tuesday.
Meanwhile, South Korea's Defense Ministry said in a briefing that, "considering the North Korean leader Kim Jong Un has been accompanied by many military officers, in particular, we are closely monitoring if there will be negotiation between North Korea and Russia over the arms trade and technology transfer."
Describing the Kim-Putin summit as "just the tip of a dangerous iceberg," Teneo Intelligence advisors Victor Cha and Andrius Tursa noted that "ties between the two seemed to accelerate quickly in the past two months" .
"Near-term, one major concern is whether Russian cooperation will extend to supplying new ballistic missile technology to North Korea, something the Kim regime desires even above food imports for its citizens," the analysts said in a research note last week.
"The trajectory of this cooperation suggests that Moscow could continue to help Pyongyang enhance its missile arsenal," they said, adding that an immediate concern is whether Russia will supply missile technologies in return for more North Korean weapons longer term.
Any "aggressive military posturing could ignite a crisis on the Korean peninsula," they added, and make "life difficult for the U.S. and its partners, who have few efficacious tools with which to respond to the emerging axis."
In late August, U.S. National Security Council spokesman John Kirby said the U.S. had evidence that North Korea had provided rockets and artillery to the Russian mercenary group Wagner "months ago," adding that Moscow had continued to canvas for more munitions.
"We urge the DPRK [Democratic People's Republic of Korea] to cease its arms negotiations with Russia and abide by the public commitments that Pyongyang has made to not provide or sell arms production," Kirby said. "And of course, we'll take action directly by exposing and sanctioning individuals and entities working to facilitate arms deals between these two countries."
He noted, however, that as yet, the U.S. has not seen Pyongyang provide weapons directly to Moscow.
"We will see how it goes," Kirby said, adding that the U.S. does not have formal diplomatic relations with North Korea and therefore will continue to issue warnings publicly.
