South Korea, Japan and the U.S. are rushing to address the increasingly plausible scenario that Pyongyang is sending combat troops to fight with Russian forces in its war against Ukraine, with Seoul reportedly considering supplying Kyiv with offensive weapons.

On Tuesday, Seoul urged “the immediate withdrawal” of any North Korean troops, saying it would “implement a phased response" if military cooperation between Moscow and Pyongyang continues.

“We will not sit idly by, and will respond resolutely together with the international community,” the South Korean Presidential Office said in a statement following a meeting of the country’s National Security Council.