South East Asian leaders have started annual talks set to focus on territorial rows, a declaration on human rights and deadly ethnic unrest in Myanmar.
The Association of Southeast Asian Nations summit follows months of acrimony within the 10-member bloc over how to handle disputes with China over rival claims in the South China Sea.
Some of the talks will include US President Barack Obama and Chinese Premier Wen Jiabao.
ASEAN leaders are also aiming to use the talks in Phnom Penh in Cambodia to push forward a planned giant free trade zone with China, Japan, South Korea, India, Australia and New Zealand.
Negotiations for the free trade area, which would account for roughly half the global population and around a third of the world's annual gross domestic product, are set to be officially launched on Tuesday.