SEOUL - North Korea on Sunday criticized for a second day a U.S. decision to send tanks to Ukraine, calling it an "unethical crime" aimed at perpetuating an unstable international situation.

Washington's allegations that North Korea has provided arms to Russia are a "groundless rumor" to justify its own military aid to Ukraine, Kwon Chung-keun, director of U.S. affairs at North Korea's Ministry of Foreign Affairs, said in a statement carried by state news agency KCNA.

"The U.S. is working hard to supply such offensive weapons as (main battle tanks) to Ukraine at any cost in disregard of the just concern and criticism of the international community," the statement said. "This is an unethical crime aimed at keeping the international situation unstable."

The baseless claims of North Korea-Russia arms deals are a "grave provocation that can never be allowed" and perpetuating them will bring a "really undesirable result", Kwon added.

On Saturday North Korean leader Kim Jong Un's powerful sister, Kim Yo Jong, denounced U.S. pledges of battle tanks to Ukraine, claiming Washington was "further crossing the red line" to win hegemony by proxy war, KCNA reported.

Nuclear-armed North Korea launched an unprecedented number of missiles last year, including intercontinental ballistic missiles (ICBMs) capable of reaching the U.S. mainland. U.S. and South Korean officials have also warned the North could be preparing for its first test of a nuclear device since 2017.

The White House said in December that North Korea completed an initial arms delivery of infantry rockets and missiles to a private Russian military company, the Wagner Group, to shore up Russian forces in Ukraine.

(Reporting by Josh Smith; Editing by Cynthia Osterman)