Terrorism inspired by the Islamic State group is of increasing concern in the region. Eight people were killed during assaults last month in Indonesia's capital, Jakarta, the first major attack there in six years. Police said the attackers were linked to IS.
Singapore, Malaysia and Indonesia, the world's most populous Muslim nation, have all reported citizens travelling to fight in Iraq and Syria, and several small militant groups in the Philippines have pledged allegiance to IS.
Obama also plans to raise the issue of good governance and adherence to the rule of law. Asean members run the gamut of political systems, from open democracies in Indonesia and the Philippines to communist governments like Vietnam and Laos that ban political dissent.
Human rights advocates have faulted the US for inviting unelected leaders, like Thai Prime Minister Prayut Chan-o-cha, who seized power in a May 2014 coup. Cambodia's Hun Sen, who has used violence and intimidation against political opponents, is making his first official US visit during his 31-year tenure as prime minister.
Four of the leaders attending are "lame ducks", like Obama, with little time left in office. One of them, Myanmar's Thein Sein, skipped the summit entirely and and sent a deputy instead.