New York, New York - Washington and its allies challenged North Korea at the United Nations on Friday over claims Pyongyang is breaching arms control measures by supplying weapons to Russia to use in its war in Ukraine.

Washington's deputy envoy to the UN Robert Wood hit out at what he said were "unlawful arms transfers from the DPRK (North Korea) to Russia" as the two sides forge ever closer ties.

"We condemn in the strongest possible terms, those unlawful transfers, which have significantly contributed to Russia's ability to conduct its war against Ukraine," Wood said ahead of a UN Security Council meeting on the issue.

The supply of arms and munitions by North Korea violates Security Council resolutions on the issue from 2006, 2009, and 2016, he said.

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Jonah Leff, executive director at Conflict Armament Research which tracks the use of weapons in war, told the Security Council that CAR had found evidence of North Korean ballistic missile use in Ukraine – in breach of sanctions.

"A CAR field investigation team physically documented the remnants of a ballistic missile that struck Kharkiv on January 2, 2024," that he said investigators concluded was North Korean-made "based on several unique features."

Leff said identical missiles had also struck Kyiv and Zaporizhzhia earlier this year.

Russia's UN ambassador Vasily Nebenzya denied Moscow had sought to undermine sanctions, and opposed the presence of Ukraine and the European Union at the meeting.

Ties between Moscow and Pyongyang have grown rapidly in recent years, with the North Korean leader Kim Jong Un hosting Russian President Vladimir Putin earlier this month and signing a mutual defense agreement.

Tensions are high on the peninsula with South Korea alarmed at Moscow's embrace of its neighbor, and the North responding to balloons carrying pro-Seoul propaganda with its own balloons carrying trash southward.

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Wood said China could do more to prevent growing military ties between Russia and North Korea. That drew a rebuke from Beijing's UN ambassador who said "the US must reflect deeply – especially on its own actions instead of blaming others" for growing tensions on the peninsula.

Pyongyang tested a ballistic missile on June 25, which Wood said showed "contempt" for the Security Council.

Washington has long claimed that Russia is using up munitions and losing heavy equipment in Ukraine, forcing the Kremlin to turn to its small pool of allies, including North Korea, for support.

North Korea's UN ambassador Kim Song told the Security Council there was "no reason whatever to be concerned" and the agreement signed between Moscow and Pyongyang was to "promote progress" in relations.

Washington was joined by allies France and the UK in its condemnation of what it says are sanctions-busting arms shipments from North Korea to Russia.

Putin has slammed the US for its ongoing military support for Ukraine, saying last week that he "does not rule out" sending weapons to North Korea.