SEOUL, South Korea — South Korea said Thursday that it would consider sending arms to Ukraine, a major policy change that was suggested after Russia and North Korea rattled the region and beyond by signing a pact to come to each other's defense in the event of war.

The comments from a senior presidential official came hours after North Korea's state media released the details of the agreement, which observers said could mark the strongest connection between Moscow and Pyongyang since the end of the Cold War. It comes at a time when Russia faces growing isolation over the war in Ukraine and both countries face escalating standoffs with the West.