China on Friday began work on its second west-to-east natural gas transmission pipeline, which will mainly carry natural gas from Turkmenistan and China's Xinjiang Uygur Autonomous Region  to the Yangtze and Pearl River Deltas, the country's two most developed regions.

Construction of the 9,102-kilometer gas pipeline, which consists of a main line and eight sub-lines, will cost an investment of 142.2 billion yuan ($20 billion).

With a designed gas transmission capacity of 30 billion cubic meters per year, the pipeline would traverse 12 provinces and autonomous regions before reaching eastern municipality of Shangha and southern Guangdong Province.

The main line extending 4,843 km would start from Khorgos in the northwestern Xinjiang to Guangzhou, capital of Guangdong Province.

The western segment of the main line  will go into operation by 2009, and the eastern segment by the end of June in 2011, said Jiang Jiemin, general manager of China National Petroleum Corporation.

The first massive project to pipe natural gas from the west to the east was put into commercial operation at the end of 2004, starting from the Tarim Basin of Xinjiang and arriving in Shanghai.

The pipeline extending 4,000 km traverses 10 province-level regions, with designed annual gas transmission capacity of 12 billion cubic meters, which can ensure a stable gas supply of 30 years.