South Korea warns it could reopen discussions over arms supplies to Ukraine if Pyongyang and Moscow continue to build military ties.

South Korea has vowed to take measures to counter military cooperation between Russia and North Korea, despite denials from Pyongyang that it has sent troops to support Moscow’s war against Ukraine.

Officials in Seoul said Tuesday that the Russia-North Korea alliance poses an international threat and vowed that South Korea will work with its allies to take countermeasures, possibly including supplying weapons to Ukraine.

South Korea summoned Russia’s ambassador on Monday after accusing North Korea of ​​sending 1,500 soldiers to fight alongside Moscow’s forces in Ukraine. North Korea dismissed Seoul’s claim as “baseless rumours”, but Seoul pushed that aside on Tuesday and promised action.

“Sending troops to Russia’s illegal war of aggression in Ukraine is a significant security threat not only to our country but also to the international community,” the National Security Council said.

“Following the deployment of North Korean combat troops, the government will implement countermeasures in phases,” it added.

A senior official in President Yoon Suk-yeol’s office said diplomatic, economic and military measures were being prepared, adding that South Korea could reverse its earlier decision not to send weapons to Kiev.

Seoul has been under pressure from some Western countries and Kiev to supply Ukraine with lethal weapons, but has so far focused on non-lethal aid, including demining equipment.

“We would consider providing weapons for defensive purposes as part of the step-by-step scenarios, and if it looks like they go too far, we may also consider offensive use,” the official told reporters.

North Korea has in recent months denied accusations from the South and the United States that it has supplied weapons to Russian forces.

Late on Monday, the country rejected the South Korean spy agency’s claim that it has now sent special personnel to Russia’s Far East for training in preparation for deployment to Ukraine.

“Regarding so-called military cooperation with Russia, my delegation does not feel the need to comment on such baseless, stereotypical rumors,” a North Korean representative said during a committee meeting at the UN General Assembly.

Seoul’s accusations, the official said, are “aimed at smearing (North Korea’s) image and undermining the legitimate, friendly and cooperative relations between two sovereign states.”

Russia has not confirmed Pyongyang’s troop deployment, but defended its military cooperation with the North, saying on Monday that it is “not against the interests of South Korean security.”

Pyongyang and Moscow have been allies since North Korea’s founding, and Russia’s large-scale invasion of Ukraine in 2022 has brought them closer.