The agreement, which was originally made in September 2004, will see Gazprom acquire Rosneft. In return, the Russian government will boost its 39% interest in Gazprom to a controlling 51% stake.

Having formed a state-owned energy champion with majority control, Vladimir Putin’s government will then allow foreign trading in Gazprom shares.

The merger had been put on hold after Rosneft acquired Yuganskneftegas and its prize oil fields at a disputed auction last year. Despite company opposition, Yukos’s core unit had been put up for sale after the state had claimed back taxes of some $28 billion. With Yuganskneftegaz to remain as a standalone company, headed by current Rosneft CEO Sergei Bogdanchikov, Gazprom is not expected to be liable to any litigation brought by Yukos.

Even without Yuganskneftegaz, Gazprom and Rosneft will rank as Russia’s fifth largest oil producer and Gazprom is already the largest gas company in the world. The combination of the assets of Gazprom and Rosneft will create one of the biggest oil and gas majors in the world.