WASHINGTON, United States -- The White House warned Tuesday that North Korea would "pay a price" if it supplies Russia with weaponry for its war in Ukraine, with Kim Jong Un and Vladimir Putin expected to hold talks on the issue.

Sanctions-hit Russia is reportedly eager to secure more military supplies from its ally to bolster its forces as Kyiv pushes a highly scrutinized counteroffensive to take back its territory.

US President Joe Biden's national security advisor Jake Sullivan said Pyongyang and Moscow were eyeing "leader level discussions, perhaps even in person" on Russia's arms needs.

Sullivan said Russia could use weapons from North Korea to attack food supplies and heating infrastructure heading into winter to "try to conquer territory that belongs to another sovereign nation."

"This is not going to reflect well on North Korea and they will pay a price for this in the international community," he added.

Sullivan added that it "says a lot that Russia is having to turn to a country like North Korea."

Russian Defense Minister Sergei Shoigu traveled to North Korea in July seeking to acquire additional munitions for the war, the White House said.

The Kremlin said on Tuesday it was unable to confirm a summit between Putin and Kim. "We have nothing to say on this," Kremlin spokesman Dmitry Peskov said.

Shoigu said on Monday that Russia was considering joint military drills with North Korea. "Why not? They are our neighbors," he was quoted as saying by the TASS news agency.

- Secret talks -

The United States warned last week that Russia was already in secret talks with the North to acquire a range of munitions and supplies for Moscow's war effort.

Kim is likely to head by armored train later this month to Vladivostok, on Russia's Pacific coast not far from North Korea, to meet Putin, US and other officials told the New York Times.

Vladivostok is hosting the Eastern Economic Forum from September 10–13, which was attended by representatives from 68 countries last year.

According to the Times, Putin is seeking artillery shells and antitank missiles from North Korea, while Kim, who could even travel to Moscow, is reportedly in search of advanced technology for satellites and nuclear-powered submarines, as well as food aid for his impoverished nation.

An official at Seoul's unification ministry, which handles inter-Korean relations, said various developments indicated the growing possibility of an arms deal between Pyongyang and Moscow.

"Any form of cooperation between North Korea and neighboring countries must be conducted in a way that does not undermine international norms and peace," he told reporters.

Washington said last week that, despite its denials, North Korea supplied infantry rockets and missiles to Russia in 2022 for use by the privately controlled Wagner military group.

- Diplomatic isolation -

Park Won-gon, a professor at Ewha University in Seoul, said a summit between the leaders of diplomatically isolated Russia and North Korea would send a message to Washington, which is ramping up defense cooperation with South Korea and Japan.

"North Korea and Russia also need to showcase their cooperation in a symbolic diplomatic sense," he told AFP.

Last week at the United Nations, the United States, Britain, South Korea and Japan said that any deal to increase cooperation between Russia and North Korea would violate Security Council resolutions forbidding arms deals with Pyongyang -- resolutions Moscow itself had endorsed.

They said another group of Russian officials traveled to North Korea for follow-up talks after Shoigu's visit to Pyongyang.

Cho Han-bum, a senior research fellow at the Korea Institute for National Unification, said sanctions will do little to stop Russia and North Korea from trading weapons.

"The war in Ukraine and the strategic competition between the United States and China have virtually neutralized the current UN Security Council system," Cho told AFP.

The United States last month sanctioned three entities accused of seeking to facilitate arms deals between North Korea and Russia as Washington tightened restrictions on support for Moscow's war in Ukraine.

Ukrainian officials have claimed some progress in their counteroffensive, but Putin said again on Monday the attempt to retake land lost since Russia's February 2022 invasion had been unsuccessful.

"It is not that it is stalling. It is a failure," Putin said during a news conference with Turkish leader Recep Tayyip Erdogan in the Black Sea resort city of Sochi.