The Pluto approval included environmental conditions to protect threatened and migratory species, ecological communities and the marine environment, Australian Environment Minister Malcolm Turnbull said in a statement.

Perth-based Woodside's board gave the go-ahead in July for Pluto, which will be Western Australia's first liquefied natural gas (LNG) project in 22 years and cost nearly US$2 billion above estimates due to industry cost pressures.

The board also gave approvals to begin studies on the possible expansion of Pluto, by the addition of a second and third train, as well as a domestic gas facility to supply the Western Australian market.

Analysts see the Pluto project, which will more than double Woodside's LNG output, as a key development to underpin the company's long-term growth.

Woodside, which is 34 percent-owned by Royal Dutch Shell Plc said in July the Pluto project had been sanctioned subject to environmental and other approvals from the state and federal governments, which it expected to receive soon.

Australia has five other LNG projects in varying stages of development, such as BHP Billiton's proposed Scarborough development, Woodside's Browse and Sunrise fields, Japanese INPEX's Ichthys field and Chevron's giant Gorgon project.

The Pluto project, estimated to hold 5 trillion cubic feet of gas, will have a processing capacity of 4.8 million tonnes per annum (mtpa) and is targeting first deliveries to Japanese customers Kansai Electric Power Co. and Tokyo Gas Co. Ltd. by late 2010.

Woodside plans to build an onshore LNG processing plant on the Burrup Peninsula in northwestern Australia to process gas from Pluto field and from other suppliers.

The facility will have a processing capacity of 5-6 mtpa for Pluto gas, but approvals have been sought for up to 12 mtpa to allow for expansion.

Environmental activists have complained the project will place at risk prehistoric Australian rock carvings up to 30,000 years old on the Burrup Peninsula.

Turnbull said environmental conditions included a management plant to ensure threatened species of sea snakes and sea turtles were not harmed by the planned LNG processing facility.