Russia and China have signed a memorandum of understanding to supply gas from western Siberia to China, in the second big gas deal to be sealed this year as President Vladimir Putin builds investment ties with China to counter increasing isolation from the west.

The framework agreement between China National Petroleum Corporation and Russian energy group Gazprom is for an additional 30bn cubic metres of gas per year. It follows a $400bn agreement in May for Russia to sell up to 38bcm of gas per year from eastern Siberia to northeastern China.

The deals represent welcome diplomatic and financial support for Mr Putin, whose regime is under fire from the west over its support for Russian separatists in Ukraine. Energy exports are Russia’s primary source of hard currency and the expectation is that the Chinese would help with the expensive task of building and financing the pipelines.