The White House claimed that North Korea provided Russia with ballistic missiles, which were used in the country's war against Ukraine.
"This is a significant and concerning escalation," National Security Council spokesman John Kirby told reporters in a briefing.
Russian forces launched at least one of the North Korean-supplied missiles on Dec. 30, which landed in an open field in the Zaporizhzhia region, Kirby said.
Moscow's forces then fired "multiple" ballistic missiles into Ukraine as part of a mass aerial attack on Jan. 2, he added.
The United States and its allies will now raise the matter at the U.N. Security Council as it represents a breach of U.N. sanctions against North Korea, said Kirby.
Russia also intends to purchase missiles from its ally Iran, said the spokesman.
In September, North Korean leader Kim Jong Un voiced full support for President Vladimir Putin and Russia during a meeting in Uglegorsk.
