Inpex Corp., the nation's largest energy explorer, said Friday it has signed an initial planning contract with JGC Corp., Chiyoda Corp. and KBR Inc. of the United States for its $20 billion liquefied natural gas plant project in Darwin, Australia.

Design and planning work will be carried out this year with production slated to begin in late 2014 or early 2015, Tokyo-based Inpex said in a statement to the stock exchange.

The plant, capable of producing at least 8 million metric tons of LNG a year, will process natural gas from the Ichthys field off northwestern Australia via a proposed 850-km pipeline. The fuel will be shipped to Japan, the world's biggest LNG consumer.

The deal puts the three firms in a strong position to win a construction contract if Inpex and partner Total SA go ahead with the plant, JGC spokesman Hideyuki Mizuno said.

"The three of us will spend at least a year on this initial engineering work," he said by phone from Tokyo. "I don't think Inpex will kiss us goodbye and ask other engineers to come in and build the plant."

JGC will lead the initial engineering, Inpex spokesman Kazuya Honda said by telephone from Tokyo, declining to disclose the cost of the first phase. Inpex and Total will decide whether to go ahead with the Ichthys exploration project late this year or early 2010, according to the statement.

The Ichthys project also entails building facilities to produce 100,000 barrels a day of condensate, a type of light crude oil, and 1.6 million tons of liquefied petroleum gas.