President Park Geun-hye and leaders from the 10 ASEAN member states will meet at a special summit scheduled for mid-December, mostly likely in Busan.
The government on Thursday discussed the venue and timing of the summit.
A diplomatic source in Seoul said, "Some ASEAN states prefer a warmer place than Seoul for the summit, so the Korean government is considering Busan."
The summit marks the 25th anniversary of dialogue between the two sides and is the first multilateral summit to be held here since the inauguration of the Park administration.
The first special Korea-ASEAN summit was held in Jeju in 2009.