Lloyd Austin visits Ukraine as Zelenskyy warns of 'clear' North Korea threat

Secretary of Defense Lloyd Austin arrived in Kyiv, Ukraine, on Monday morning for his third visit to the country since Russia's full-scale invasion began in 2022.

The Pentagon said in a statement that Austin "will meet with Ukrainian leadership and underscore the U.S. commitment to providing Ukraine with the security assistance it needs to defend itself from Russian aggression on the battlefield."

Austin will end his fourth visit to Ukraine as defense secretary with an address on Kyiv's successes, American commitment to supplying its troops and -- with just over two weeks until the U.S. presidential election -- "why Ukraine's fight matters for U.S. security," the Pentagon said.

Austin announced another $400 million in military aid to Ukraine while meeting with President Volodymyr Zelenskyy on Monday. The package included rocket and tube artillery ammunition, armored vehicles and a variety of anti-tank weapons, according to a Pentagon press release.

A senior defense official told ABC News that Austin's visit is intended as an opportunity to consider the overall status of the war, plus to underscore the U.S. role in defeating Moscow's strategic objectives and inflicting "astronomical casualties" on Russian forces.

Austin was scheduled to meet with Zelenskyy and Defense Minister Rustem Umerov, the official said, with the former's "victory plan" among the planned topics of conversation.

Ukraine, the senior U.S. official said, is in a stronger position now than one year ago, although battlefield conditions are difficult.

Kyiv's forces are being slowly pushed back in the east of the country, while Russian counter-offensives are chipping away at Ukraine's pocket of seized territory in the western Russian Kursk region.

Meanwhile, Russian drone and missile attacks continue across the country. The strikes have been particularly punishing for the country's battered energy grid in the lead up to winter.

Manpower also remains a constant strain, and conversations continue in Ukraine about lowering the minimum conscription age from 25 to 18 to bolster available troop numbers.

Conscription is a politically sensitive topic, and April's decision to drop the minimum age from 27 to 25 followed almost a year of debate.

Ukraine, the defense official said, should be able to take advantage of strategic opportunities as they arise. The challenge is in how to best its synchronize forces and prioritize its goals, they added.

Austin arrived shortly after Zelenskyy said Ukraine had "clear data" showing that North Korea is supplying Russia with military personnel.

"A new threat has emerged -- the malign alliance between Russia and North Korea," Zelenskyy said in a video statement posted to social media on Sunday evening.

"These are not just workers for production, but also military personnel," the president said. "We expect a proper and fair response from our partners on this matter."

"If the world remains silent now, and if we face North Korean soldiers on the front lines as regularly as we are defending against drones, it will benefit no one in this world and will only prolong this war," Zelenskyy said.

Lt. Gen. Kyrylo Budanov -- the head of the Ukrainian Defense Ministry's Main Directorate of Intelligence -- said there are now "nearly 11,000 North Korean infantry troops training in eastern Russia to fight in Ukraine."

Budanov said the troops will be ready to join battle by Nov. 1, the first group of around 2,600 soldiers earmarked for the fighting in Kursk.

South Korea's spy agency warned last week that 1,500 North Korean soldiers were already inside Russia, in what it described as a "grave security threat."

Kremlin spokesperson Dmitry Peskov dismissed foreign concerns about deepening bilateral ties. "There is a lot of contradictory information, and that is probably how it should be treated," he said, describing North Korea as a close neighbor and partner.

"This should not cause anyone any concern, because this cooperation is not directed against third countries," Peskov added.

ABC News' Britt Clennent, Lauren Minore, Yulia Drozd, Guy Davies and Matthew Seyler contributed to this report.