MOSCOW — North Korea will stand by Russia until its victory in Ukraine, Pyongyang's top diplomat said in Moscow on Friday, as the United States warned that thousands of North Korean troops could be sent to fight in the Russia-Ukraine war in the coming days.

North Korea Foreign Minister Choe Son Hui is on a visit to the Russian capital as the West believes up to 10,000 North Korean troops are on the brink of entering the ongoing conflict on Russia's side.

US intelligence has said some North Korean forces have made their way to Russia's Kursk border region, with Washington and Seoul urging Pyongyang to withdraw its troops.

"We will always stand firmly by our Russian comrades until victory day," Choe declared in Moscow after talks with her Russian counterpart Sergey Lavrov.

She said North Korea had no doubt in the "wise leadership" of President Vladimir Putin, who signed a mutual assistance pact with Pyongyang this summer and massively warmed ties with the reclusive state.

Choe praised Moscow's war in Ukraine as a "sacred struggle."

She also vowed that North Korea will continue to develop its nuclear arsenal, with Pyongyang widely suspected of wanting nuclear technology from Russia in exchange for military support.

Neither country has denied the troop deployment reports, which Choe and Lavrov did not mention in their statements after their talks.

Lavrov did, however, laud "very close ties" between the two countries' "armies and special services."

"This will also make it possible to solve significant security tasks for our citizens and yours," he said, without giving details.

Moscow 'deeply grateful'

Lavrov also said Russia was "deeply grateful" for North Korea's "principled stance" on Ukraine.

North Korea and Iran have emerged as Russia's main backers in Ukraine, with both believed to be supplying Moscow with military hardware.

"I really appreciate today's opportunity to talk frankly in a comradely manner," Lavrov said, evoking Soviet-style language.

Russia has resuscitated its Soviet-era relations with North Korea since sending troops to Ukraine, glorifying the two countries' past standoff against the West.

Lavrov and Choe unveiled a plaque at Moscow's Yaroslavsky railway station in honor of North Korea's then-leader Kim Il Sung traveling to Moscow in 1949 to seek Soviet leader Joseph Stalin's backing to invade the South.

In a ceremony that included an orchestra, Lavrov said the unveiling of the plaque "underscores the respect and reverence with which we treat our common history and great predecessors."

He said Putin and North Korea's current leader Kim Jong Un now aim to "try to be worthy of the contribution to our friendship that was made by our predecessors."

Western inaction hit

US Secretary of State Antony Blinken said on Thursday it had not yet seen North Korean troops deployed against Ukrainian forces, but that this could happen "in the coming days."

The US announced on Friday it would provide an additional $425 million in military aid to Ukraine, including air defense interceptors and munitions for rocket systems and artillery "to meet its most urgent needs."

In his nightly address on Friday, Ukrainian President Volodymyr Zelenskyy criticized Kyiv's allies for inaction as Ukraine pleaded for permission to fire donated long-range missiles deep into Russia.

"Now we see every site where Russia is amassing these North Korean soldiers on its territory — all their camps. We could strike preventively, if we had the ability to strike long enough," he said.

"Instead of providing the long-range strike capability that is so necessary, America is watching, Britain is watching, Germany is watching," the president added.

"Everyone is just waiting for the North Korean military to start striking at Ukrainians," he added.

Zelenskyy also criticized China, which he said could block logistics between Russia and North Korea.