The handover would grant South Korea full control of its military in the event of a conflict. But the transfer might be delayed yet again.
As part of his four-country tour of Asia, Obama will visit the Philippines Monday. He's expected to highlight the importance of security cooperation and the Philippines' strategic role in the region.
North Korea backed off its threat to block reunions of families split by the Korean War, after Secretary of State Kerry refused to budge on planned military exercises with South Korea.
Defense Secretary Hagel's comments about the North's chemical arsenal come amid new concerns over the sophistication of North Korea's nuclear weapons program.