SINGAPORE (Reuters) - Indonesia has adopted a sweeping action plan to curb greenhouse gas emissions from industry, forestry and agriculture as part of a global fight against climate change, the government said on Monday.

The programme enshrines a pledge first announced by President Susilo Bambang Yudhoyono two years ago to curb emissions growth by 26 percent from projected levels by 2020 or up to 41 percent with cash and other support from rich nations.

The voluntary targets are regarded as among the most ambitious for a developing nation and came after international pressure to curb deforestation, improve land management and boost energy efficiency in Southeast Asia's largest economy.

Yudhoyono formally signed a decree on the plan on Sept 20 after working out how major national agencies would implement it, the government said in a statement.

A major focus is slashing emissions from the forestry sector. Nearly 80 percent of Indonesia's greenhouse gas emissions come from deforestation and clearing and burning of carbon-rich peatlands.

The government says total national greenhouse gas emissions totaled 2.1 billion tonnes in 2005, roughly the same as India, and are projected to grow to 3.2 billion tonnes by 2030.

Under the plan, the forestry sector and peatlands should reduce emissions by 672 million tonnes by 2020 and up to one billion tonnes if rich nations step in with more climate cash and other aid, Indonesia's special envoy for climate change, Agus Purnomo, told Reuters.

Energy and transport would need to cut up to 56 million tonnes by 2020 based on the top reduction target and 78 million tonnes for the waste management sector.

Other areas covered are agriculture and industry and the plan lays out detailed projects that would help meet the targets for each sector.

"The plan takes into account the most realistic action plan for 5 major sectors," Armida Alisjahbana, the Minister for National Development Planning, told Reuters in an email.

"It describes the national policies and strategies for each respective sector including its budget implications and it also mandates provincial governments to translate the national action plan into provincial action plans," she said.

The government would hold regular reviews of the plan.

Big developing nations such as Indonesia, China, India and Brazil have come under increased pressure from developed countries to curb the growth of greenhouse gas emissions to try to limit global warming to 2 degrees Celsius. Above that level, scientists say the world risks "dangerous" climate change.

Developing nations now emit more than half mankind's greenhouse gas pollution, fueled by soaring demand for coal, oil and gas to power their booming economies.

(Reporting by David Fogarty; Editing by Sanjeev Miglani )