Russian oil major Lukoil has filed a suit in the Swedish courts to ensure it can acquire full control of its joint venture with Petrokazakhstan before Chinese oil company Chinese National Petroleum Corporation completes its purchase of the Kazakhstani outfit.

Having appeared to have secured its prize in August, Chinese National Petroleum Corporation’s takeover of PetroKaz faces renewed uncertainty.

The Chinese state oil producer successfully bid for the Canadian owned Petrokazakhstan company in August, beating off competition from The Oil and Natural Gas Corporation of India with a bid of $4.18 billion.

However, since the successful offer, which is expected to receive shareholder approval in the near future, an argument has erupted over preferential bidding rights.

Lukoil, which current runs a 50-50 joint venture with Petrokaz, has contested in its Swedish court filing that it has pre-emptive rights to Petrokaz shares in the venture. The Russian company wants to ensure it is given the opportunity to buy out its partner’s 50% share in the Turgai Petroleum joint venture before Petrokaz is taken over. However, counter arguments suggest that Lukoil’s claim is only relevant if Petrokaz wanted to sell its stake, not if Petrokaz was itself being sold.

Meanwhile, the Kazakhstan government has threatened to take control of the oil producer, having passed laws which state it has first refusal on oil stakes that are put on sale.