WASHINGTON: The United States said Tuesday that Russia would be violating UN resolutions if it reaches an arms deal with North Korea, after the two countries' leaders called for greater cooperation.

"Any kind of security cooperation or arms deal between North Korea and Russia would certainly violate a series of UN Security Council resolutions," State Department spokesman Vedant Patel told reporters.

Patel highlighted that Russia was relying on some of the world's most ostracized nations, North Korea and Iran, to support its "war of aggression" against Ukraine.

North Korea’s Kim, Russia’s Putin exchange letters vowing stronger ties

"Our information indicates that Russia is seeking to increase this type of military cooperation with the DPRK," he said, referring to the North by its official name, the Democratic People's Republic of Korea.

Russian President Vladimir Putin and North Korean leader Kim Jong Un both spoke of greater ties in messages Tuesday marking North Korea's National Liberation Day.

The statements follow a visit to Pyongyang by Russian Defense Minister Sergei Shoigu.