North Korea has slammed Washington's decision to supply Ukraine with tanks, claiming the US is "further expanding the proxy war" to destroy Russia.

Earlier this week, US President Joe Biden promised 31 Abrams tanks, one of the most powerful and sophisticated weapons in the US army, to help Kyiv fight off Moscow's invasion.

Along with China, Russia is one of the North's few international friends and has previously come to the regime's aid.

In a statement released late Friday, Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, blamed Washington for the crisis in Ukraine, accusing it of "further crossing the red line" by sending the tanks.

"Lurking behind this is the US sinister intention to realize its hegemonic aim by further expanding the proxy war for destroying Russia," she said in the statement.

Washington is "the arch criminal", she added, and Pyongyang will "always stand in the same trench with the service personnel and people of Russia".

"The world would be brighter, safer and calmer now if it were not for the US," she said.

Other than Syria and Russia, North Korea is the only country to recognise the independence of Luhansk and Donetsk, two Russian-backed separatist regions in eastern Ukraine.

Russia, one of the five permanent members of the UN Security Council, has long held the line against increasing pressure on nuclear-armed North Korea, even asking for relief from international sanctions for humanitarian reasons.

Kim Jong Un declared North Korea an "irreversible" nuclear state in September, and the country conducted sanctions-busting weapons tests nearly every month last year -- including firing its most advanced intercontinental ballistic missile.