Japan was expected to announce a major initiative to help keep Asia green.
The one-day East Asia Summit was being held a day after contentious debate over military-ruled Myanmar, which overshadowed the announcement of a landmark charter to eventually turn Southeast Asia into an EU-style economic bloc.
The summit includes the 10 members of the Association of Southeast Asian Nations, plus China, India, Japan, South Korea, Australia and New Zealand.
The debate over the human rights crisis in Myanmar was set aside as the leaders of the 16 countries filed into a conference room at a luxury hotel in downtown Singapore.
Climate change dominated the agenda, and the leaders are expected to issue a joint statement calling on the international community "to urgently act to address the growth of global green gas emissions."
According to the draft of the joint statement obtained by The Associated Press, the summit will call on the 16 countries to actively take part in forging a new environmental blueprint to replace the Kyoto Protocol, which expires in 2012.
Indonesia will host a conference on a successor to Kyoto next month in Bali. The Kyoto Protocol sets limits on emissions by developed nations, but the United States and Australia have refused to join it because it exempts major polluters, China and India.
Australia, the world's worst greenhouse gas polluter per capita, says its emission targets could hurt Australian industries while handing competitive advantages to developing countries.
China's booming economy has propelled it past the United States as the world's largest emitter of carbon dioxide, the atmospheric pollutant that is primarily responsible for global warming.
Two-thirds of China's power comes from coal, which releases more carbon dioxide into the atmosphere than any other energy source. Over the next five years, the country expects to complete at least one new coal-fired power plant a week.
In India, where several automakers are competing to provide affordable cars to the country's enormous middle class, there were 300,000 cars registered last year in the capital New Delhi alone.
The government acknowledges that it expects the country's carbon dioxide emissions to grow fivefold by 2031, which would put India about where the United States is now in terms of emissions.
The East Asia Summit is also expected to call on members to work to reduce by at least 25 percent their energy intensity -- the amount of energy needed to produce a dollar of gross domestic product -- by 2030.
East Asian countries also will adopt an "aspirational goal" of expanding their combined forest cover by at least 15 million hectares (37 million acres) by 2020 and fight deforestation.
Separately, Japanese Prime Minister Yasuo Fukuda was expected to unveil a major initiative to help Asian countries -- in particular China and India -- to cut back carbon emissions and combat climate change.
ASEAN's members are Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam.
Also Wednesday, UN envoy to Myanmar, Ibrahim Gambari, was scheduled to hold private meetings with leaders to brief them on the progress he has made in his talks with the junta leaders and pro-democracy leader Aung San Suu Kyi.
ASEAN leaders abruptly withdrew an invitation to Gambari to address the East Asian Summit after Myanmar objected, a diplomatic blunder that dominated the ASEAN summit on Tuesday.