Russian president delivered the warning after Seoul announced it would consider arming Kyiv.

Russian President Vladimir Putin Thursday warned South Korea that sending lethal weapons to Ukraine would be a “big mistake.”

His comments come after Seoul announced it would consider arming Ukraine in response to Russia and North Korea signing a mutual defense pact on Wednesday.

“If South Korea supplies weapons to Ukraine, it will not like the answer. I hope they won’t do it, it would be a big mistake,” Putin said at a press conference in Vietnam, where he is conducting a two-day state visit aimed at deepening strategic cooperation.