By Josh Smith SEOUL (Reuters) -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…