In a long-awaited development, the governments of North Korea and South Korea announced Monday that they would hold their first-ever presidential summit June 12 to 14 in Pyongyang. This meeting is a victory for the "sunshine" policy of South Korean President Kim Dae Jung and could fundamentally change the political dynamic in this part of the world. All nations must rally behind Mr. Kim and his efforts to build an enduring peace between the two Koreas. But there are good reasons to be cautious. There is ample time for the agreement to come unraveled.

How and why North Korea makes its decisions are unknown. That means the motives for the agreement and the timing of the announcement are unclear. But one thing is certain: It could not have been better timed for Mr. Kim. The country holds parliamentary elections Thursday, and his Millennium Democratic Party is in a dead heat with the opposition Grand National Party. The summit news is a big boost to the MDP's prospects, prompting carefully worded allegations that the government is playing politics with South Korea's national security. That cynicism is understandable, given revelations about previous attempts by the Korean security services to manipulate events on the eve of elections to strengthen the then-ruling party.

The South Korean election could have figured in Pyongyang's thinking as well. The timing could be a signal by North Korean government that it prefers the current administration in Seoul. It might also have reckoned that providing Mr. Kim with a gift of this magnitude would make him even more amenable to Pyongyang's demands at the meeting.