North Korean leader Kim Jong Un plans to visit Russian President Vladimir Putin later this month, probably in the Russian port city of Vladivostok, to discuss possible weapons deals to bolster Russia's fighting force in Ukraine, according to two senior administration officials.

White House officials did not publicly confirm that such a meeting was expected to take place but expressed growing concern over relations between Moscow and Pyongyang - and urged Kim not to move forward with the trip or sell weapons to Moscow.

Arms negotiations between the countries "are actively advancing," Adrienne Watson, a National Security Council spokeswoman, said in a statement Monday. "We have information that Kim Jong Un expects these discussions to continue, to include leader-level diplomatic engagement in Russia."

"We've worked to expose these secret talks and to warn the DPRK not to move forward," said one senior administration official, using an abbreviation for North Korea and speaking on the condition of anonymity because of the sensitivity of the matter. "If they think they can do this furtively without international awareness then they are mistaken."

The Russian state news agency Interfax did not immediately confirm the meeting but published an article citing the New York Times, which first reported the story.

Russia and North Korea, both under heavy international sanctions, have not hidden their increasingly close relationship. Pyongyang is hurting for hard currency, said the second administration official, "and they're looking for ways to buttress their foreign exchange and other earnings."

North Korea delivered infantry rockets and missiles into Russia for use by Wagner Group mercenaries last year and "continues to consider providing military support to Russia's military operations against Ukraine," according to new information, National Security Council spokesman John Kirby told reporters last week.

In July, Russian Defense Minister Sergei Shoigu visited Pyongyang, pledging to boost ties between the two nations and trying to persuade Pyongyang to sell artillery munitions to Moscow, Kirby said. It was the first time a Russian defense minister had visited Russia's southern neighbor since the Soviet Union's collapse.

Shoigu toured an exhibition of North Korea's banned ballistic missiles. He told Interfax on Monday that joint military exercises with North Korea were under discussion.

Kirby said Wednesday that Putin and Kim had traded letters following the trip.

North Korea has said repeatedly that it would not sell arms to Russia. But Kirby said that Russian officials traveled to North Korea after Shoigu's visit to continue discussions about possible arms sales, according to U.S. intelligence. Russia is looking to replenish its ammunition stocks amid signs of shortages as it staves off Ukraine's summer counteroffensive.

"Under these potential deals, Russia would receive significant quantities and multiple types of munitions" from North Korea, "which the Russian military would use in Ukraine," Kirby said. "These potential deals also could include the provision of raw materials that would assist Russia's defense industrial base." Any such arrangement would violate U.N. Security Council resolutions, he added.

The United States continues to impose new sanctions targeting both countries, including measures last week, in concert with Japan and South Korea, aimed at a Russian firm accused of connections to North Korea's weapons programs.

Kim does not leave North Korea frequently. He met with President Donald Trump in Singapore in 2018 and in Hanoi in 2019. He has also traveled to China, and in 2019 he met with Putin in Vladivostok.

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Toluse Olorunnipa contributed to this report.

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