The two-day summit is taking place in the capital, Phnom Penh.
Foreign ministers of the 10-member Association of Southeast Asian Nations, meeting ahead of their heads of state, have expressed concern over Pyongyang’s plans to launch a rocket in April.
They also gave Sunday’s ”orderly” vote in Burma a strong endorsement.
Asean agreed last November that Burma could take the chair of the regional bloc in 2014.
North Korea’s planned rocket launch between 12 to 16 April – which it says will put a satellite in orbit to mark the centenary of late leader Kim Il-sung’s birth – has also emerged as a key issue for the summit.
Asean was set up on 8 August 1967 by founder members Thailand, Indonesia, Malaysia, the Philippines and Singapore. Brunei joined in 1984, followed by Vietnam in 1995, Laos and Burma in 1997 and Cambodia in 1999.
The summit’s main agenda on Tuesday is its goal of becoming a EU-like bloc by 2015. Asean Secretary-General Surin Pitsuwan said the group is ”on track” to meet the deadline