BEIJING -- The trunk line of China's second West-East natural gas pipeline project will be ready to start operating at the end of this month, an official with China National Petroleum Corporation (CNPC) said Wednesday.

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Eight sub-lines are scheduled to be completed by June of next year, Liao Yongyuan, vice president of CNPC, the country's largest oil and gas producer, told Xinhua.

After completion, the 142.2-billion-yuan ($21.88 billion) pipeline project will carry 30 billion cubic meters of natural gas annually from central Asia and northwest Xinjiang Uygur autonomous region to the Yangtze and Pearl River deltas.

The project traverses 15 provincial regions and is set to bring clean energy to more than 400 million Chinese people, Liao said.

According to the country's development plan, there will be a third west-to-east gas pipeline project, which is expected to take more than 20 billion cubic meters of natural gas annually from central Asia, he said.

"There will be a fourth or even fifth gas pipeline in the future," he said, noting they are intended for domestic natural gas fields.

China's first west-to-east pipeline, which pipes gas from Tarim Basin of Xinjiang to Shanghai, is designed to transmit 12 billion cubic meters of natural gas annually.