Keith Johnson writes:  Russia and China took a giant step toward closer economic and political ties with an agreement on another massive energy deal that promises to tighten the bear hug between Moscow and Beijing for decades to come.

The preliminary accord, which comes just months after China and Russia inked a $400 billion natural gas deal, is a reflection of the shifting balance of power in Asia. It’s a marriage based on needs: Russia’s to break out of the isolation imposed by the West in the wake of its annexation of Crimea and China’s for reliable and affordable sources of energy.

Coupled with China’s new trade pacts with U.S. partners such as Austraia and South Korea to a push for Chinese-led development banks that can wrest financing muscle from the West — the latest gas deal shows what kind of challenges await the U.S. economic and diplomatic pivot to Asia.

Russia and China signed a memorandum of understanding on a second gas-export route from western Siberia to China’s western provinces. The 30-year accord, if consummated, would see Russia ship 30 billion cubic meters of gas to China starting in 2018 and would see Russia gain a big new customer right as it is feeling the squeeze from Western financial sanctions. Together with the deal signed in May, Russia could supply at least 68 billion cubic meters of gas annually to China, or about one-fifth of that country’s expected gas demand in 2020.

The deal is far from complete, but it shows the direction of Russia-China relations. Moscow has intensified its efforts to make a deal since the West slapped sanctions on it energy, defense and finance sectors. China too seems more enthusiastic.  China is trying to reduce the importance of coal in its energy mix.  It needs huge amounts of natural gas. While the country ramps up its own production and has gas-import deals with Central Asian countries and more than a dozen gas-importing terminals mushrooming on the coast, Russia’s massive gas fields offer a close and ready supply of clean fuel.