Construction of Line C was started in September 2012. With a designed capacity of 25 billion cubic meters per annum, Line C’s pipe diameter is 1,219mm, 152mm larger than Line A/B. The overall welding work of the pipeline was completed at the end of 2013. On May 31, 2014, at the initial station of the Central Asia-China Gas Pipeline in Uzbekistan, the gas valve was turned on to boost natural gas from Turkmenistan to Line C, indicating the new transnational pipeline jointly built by CNPC and its Central Asian counterparts has become operational.

Upon completion of all supporting facilities of Line C by the end of 2015, the overall delivery capacity of the Central Asia-China Gas Pipeline will hit 55 billion cubic meters per annum. This equals to approximately 20% of China’s annual natural gas consumption, and would substitute 73 million tons of standard coal, cutting carbon dioxide and sulfur dioxide emissions by 78 million tons and 1.21 million tons every year, respectively.

In September 2013, China signed inter-governmental agreements with Uzbekistan, Tajikistan, and Kyrghyzstan respectively on Line D project. On March 4, 2014, CNPC's subsidiary Trans-Asia Gas Pipeline Company Limited signed an agreement with Tajiktransgaz on jointly establishing a natural gas pipeline company to manage the construction of Line D. On August 19, CNPC and Uzbekneftegaz signed an agreement on Line D of the Central Asia-China Gas Pipeline in Uzbekistan. Under the agreement, CNPC and Uzbekneftegaz will establish a JV company to construct and operate the Uzbekistan section of Line D. On September 13, construction of the Tajikistan section of Line D started. Totaling 1,000km with 840km outside China, Line D has a designed annual deliverability of 30 billion cubic meters, and is routed via Uzbekistan, Tajikistan and Kyrgyzstan to China. Upon the operation of Line D, the Central Asia-China Gas Pipeline will have an annual deliverability of 85 billion cubic meters, the largest gas transmission system in Central Asia.