Two months ago Exxon invited companies including China National Petroleum Corporation's engineering arm to bid for construction contracts by October, sources with knowledge of the matter said.

A final investment decision is due in 2019, they said.

The project is being jointly developed with Rosneft using gas from the Sakhalin-1 venture which will be chilled into liquid to underpin the LNG plant's initial annual output target of 6 million tonnes.

Western sanctions forced Exxon to exit some joint ventures with Rosneft in late February, but LNG is not part of the sanctions. The Russian company said the move would not affect the Sakhalin-1 oil and gas production-sharing JV struck in the mid-1990s.

"The Sakhalin-1 consortium continues to explore every opportunity to monetise Sakhalin-1 gas resources," Exxon spokeswoman Julie King said.

"A liquefied natural gas plant is an option to maximise benefits to the consortium and the Russian state and its citizens," she added.

Exxon-Rosneft have also held discussions about feeding gas from Sakhalin-1 fields into a planned third production unit at an existing LNG plant run by Gazprom on Sakhalin Island, industry sources said.

Rosneft was not available for immediate comment.

Exxon's LNG footprint is expanding rapidly with major new projects planned in Qatar, Mozambique, Papua New Guinea and the United States as demand in China and Southeast Asia booms.

Gas accounted for 43 percent of Exxon output last year, according to BMO Capital Markets, a share set to rise as new LNG projects start up.

CHINESE UP LNG PROJECT WORK

CNPC's Huanqiu Contracting & Engineering Corp is preparing to bid for engineering, procurement and construction (EPC) contracts for Far East LNG's supporting facilities, such as storage tanks, pipelines and utilities, a source with direct knowledge of the matter said.

Chinese engineering companies, banks and shipyards are all muscling into LNG, typically the preserve of Western, Japanese and South Korean players, as government coal-to-gas switching policies make LNG an increasingly strategic fuel.

For example, Chinese investment is pouring into African floating LNG projects, import terminals, tankers and traditional land-based plants such as the $12 billion invested in Russia's Yamal facility, used to skirt Western sanctions.

Loans in turn drum up business for Chinese engineering firms and shipyards in LNG, and give state-backed companies the upper hand in supply negotiations.

It is unclear if Chinese lenders will help finance Far East LNG.

The bid deadline for EPC contractors is September 30, sources said.

A consortium of Japan's JGC and Texas-headquartered Fluor Corp will handle the core work of project managing and building the liquefaction trains and other key components, industry sources said.

JGC was not available for immediate comment and Fluor declined to comment.

(Writing by Oleg Vukmanovic, additional reporting by Vladimir Soldatkin in Moscow and Ron Bousso in London, editing by Veronica Brown and Jason Neely)

By Chen Aizhu and Oleg Vukmanovic