US Secretary of State Antony Blinken announced on Thursday that the U.S. State Department has imposed sanctions on one individual and three Russian entities engaged in transferring and testing North Korea’s ballistic missiles, intended for use by Russia against Ukraine.

The entities and individual subject to US-imposed sanctions include the 224th Flight Unit State Airlines, a state-owned enterprise separated from Russia’s Air Force; Vladimir Vladimirovich Mikheychik, the General Director of 224th Flight Unit State Airlines; Vladimirovka Advanced Weapons and Research Complex, a Russian military facility engaged in missile testing; and Ashuluk Firing Range, a Russian missile testing range. This is the first time the US has imposed sanctions on parties involved in the trading of ballistic missiles between North Korea and Russia.

In the statement, Blinken said North Korea’s “transfer of ballistic missiles to Russia supports Russia’s war of aggression, increases the suffering of the Ukrainian people, and undermines the global nonproliferation regime.” Blinken continued, saying the US “will not hesitate to take further actions.”

This move follows a joint statement by the US and its allies on January 9, denouncing arms transfers between North Korea and Russia, specifically criticizing Russia’s acquisition of North Korean ballistic missiles and their subsequent deployment against Ukraine on December 30 and January 2. Since the onset of the Ukraine conflict, Moscow and Pyongyang have strengthened their ties, though both parties deny engaging in any arms agreements. North Korean leader Kim Jong Un held a meeting with President Vladimir Putin in Russia’s Far East region last September, and high-ranking Russian officials have undertaken multiple visits to Pyongyang. The White House alleged last week that Russia used short-range ballistic missiles (SRBMs) obtained from North Korea to carry out numerous attacks on Ukraine, citing recently declassified intelligence.

Since its first nuclear test in 2006, North Korea has been subject to a United Nations arms embargo. Resolution 1718, passed by the UN Security Council, with the backing of Russia, prohibit nations from engaging in the trade of weapons or any other military equipment with North Korea.