It would be a "dangerous and highly concerning development" if North Korea was sending troops to help Russia in Ukraine, the United States said on Monday as South Korea and Britain warned of the high price Moscow would likely have to pay Pyongyang.

Russia's ties with North Korea have grown since the start of the Ukraine war on February 24, 2022, particularly as Moscow faces increasing international isolation. In March, Russia vetoed a United Nations Security Council resolution, effectively ending international monitoring of sanctions against North Korea.

He outlined the five-point plan to Ukraine’s parliament on Wednesday without disclosing confidential elements that have been presented in private to key allies, including the United States.