China's Xi Jinping at a regional summit signed a deal to build a gas pipeline through the impoverished ex-Soviet country of Tajikistan, Tajik television reported on Saturday.
The pipeline will transport gas from energy-rich Turkmenistan to China in as part of a huge supply deal.
"Carrying out this project will allow us to attract more than $3 billion of direct investments from Chin into the economy of Tajikistan," said the press service of Tajik President Emomali Rakhmon.
It will supply China with 25-30 billion cubic metres of oil per year, the press service said.
China is eyeing the vast oil and gas resources of ex-Soviet Central Asia for its fast-growing domestic economy and is also keen to assert political influence in a region that was dominated by Moscow for decades.
Xi and Putin met at a regional security conference held by the Shanghai Cooperation Organisation in Bishkek.
The new pipeline is due for completion in 2016 and will run for more than 400 kilometres (250 miles) within Tajikistan.
The mountainous country is the poorest ex-Soviet republic and dependent on remittances from its nationals doing manual labour in Russia.
Xi is carrying out a four-nation tour of Central Asia.