The pipeline marks a major victory for Beijing in its drive for energy supplies
China's President Hu Jintao has opened a new pipeline that will deliver gas from Turkmenistan to his country.
He was joined by the leaders of the Central Asian countries through whose territory the pipeline passes.
Analysts say the pipeline marks a major advance of Beijing's influence in the region and a step forward in its drive for increased energy security.
The new pipeline also breaks Russia's long-standing stranglehold on Turkmenistan's vast gas supplies.
"China is positive about our co-operation and the opening of this gas pipeline is another platform for collaboration and co-operation between our friendly nations," Mr Hu said.
He turned a wheel to symbolise the opening of the 1,800km (1,100 miles) pipeline, which runs from a gas field being developed by the China National Petroleum Corporation through Uzbekistan and Kazakhstan to Xinjiang in western China.
The pipeline is expected to deliver 40bn cubic metres a year to China by the time it is running at full capacity in 2013.
This is about half of China's current demand, says the BBC's Michael Bristow in Beijing.
It will mean the central Asian countries - formerly part of the Soviet Union - are less dependent on Russia buying up their supplies.
"This project has not only commercial or economic value. It is also political," Turkmenistan's President Kurbanguly Berdymukhamedov told President Hu on Sunday.
"China, through its wise and farsighted policy, has become one of the key guarantors of global security."
Turkmenistan produces around 70bn cubic metres of gas annually - almost the same amount that had until recently been purchased by Russia, Turkmenistan's biggest client.
Supplies stalled following an accident in April on the main pipeline to Russia. So far the two countries have failed to agree new terms, causing Turkmenistan to lose around $1bn a month.
The incident prompted President Berdymukhamedov to announce his country's interest in developing alternative supply routes.
Turkmenistan is nearing the completion of another pipeline to Iran, and expressed an interest in supporting the EU-backed Nabucco project.
President Hu and Kazakhstan's President Nursultan Nazarbayev unveiled the Kazakh section of the pipeline in Astana on Saturday.
It is Kazakhstan's first export route that does not go through Russia.