North Korean leader Kim Jong Un expects to make a rare trip abroad to meet with President Vladimir Putin in Russia to discuss providing arms to Moscow for its war in Ukraine, the United States said Monday.

Ukraine is pushing a highly-scrutinised counteroffensive in both the south and east that Putin on Monday dismissed as a failure, though Moscow appears eager to urgently secure more military supplies to bolster its forces.

The White House's National Security Council (NSC) spokeswoman Adrienne Watson said that "arms negotiations between Russia and the DPRK are actively advancing," using an acronym for North Korea.

"We have information that Kim Jong Un expects these discussions to continue, to include leader-level diplomatic engagement in Russia," she added.

The United States last week warned that Russia was already in secret, active 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 with Putin, according to The New York Times.

The paper said Putin wanted artillery shells and antitank missiles from North Korea, and Kim could even travel to Moscow, but that was uncertain.

Kim is reported to be seeking advanced technology for satellites and nuclear-powered submarines, as well as food aid for his impoverished nation.

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.

Russian Defense Minister Sergei Shoigu traveled last month to North Korea seeking to acquire additional munitions for the war, Watson said Monday.

- Counteroffensive progress? -

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 that Moscow itself had endorsed.

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

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.

The US Treasury Department said that Russia was continuing to use up munitions and lose heavy equipment in Ukraine, forcing it to turn to its small pool of allies, including North Korea, for support.

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

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

"At least today this is what it looks like. Let's see what happens next."

News of the likely meeting between Kim and Putin came as Ukrainian President Volodymyr Zelensky said he had visited his war-torn country's frontline eastern Donetsk region, posting a video of himself meeting soldiers.

In Kyiv, Ukrainian Defense Minister Oleksiy Reznikov announced he had handed in his resignation to parliament after Zelensky called for "new approaches" to beat back Russia.

Zelensky's decision to remove Reznikov comes after several corruption scandals rocked the defence ministry, and as pressure builds over making concrete advances in the counteroffensive.