A leaked intelligence document issued by Spain’s CNI spy agency in October warns that Russia is aggressively pursuing a plan to “monopolize access to energy supplies to Europe.” The report validates what many analysts have been saying for a long time, namely that Moscow is using Russian energy companies to gain geo-strategic control over northern, central and southern Europe.

Now Russia’s largest independent oil company, Lukoil, is negotiating the purchase of a 30 percent stake in Repsol YPF SA, Spain’s largest oil company. The deal, which is valued at 5 billion euros ($6.5 billion), calls for Lukoil to buy a 20 percent stake in Repsol from Sacyr Vallehermoso SA, a debt-laden Spanish construction company, and another 10 percent stake from La Caixa, a Catalan savings bank. Lukoil is now seeking financing in order to close the deal.

News of the politically sensitive acquisition has come as a shock to many Spaniards, who now are fiercely debating the wisdom of giving effective control of their “national energy champion” to a Russian company. Analysts say the deal could lead to a full-scale takeover or break-up of Repsol, which has lagged rivals in profitability and in reserves growth in recent years. Under Spanish takeover law, a shareholder must launch an offer for the entire company once it passes the 30 percent threshold.

Spanish Prime Minister José Luis Rodríguez Zapatero had vetoed a similar deal with Lukoil in 2006. At the time, Repsol was talking with Lukoil about cross shareholdings and joint ownership of oil reserves. But those plans were abandoned after Sacyr built up its holdings in Repsol in late 2006, presumably in order to keep Repsol in Spanish hands.