UPDATE: 10/22/12, 10:00 a.m. EDT. The BBC reports that BP has agreed to sell its 50 percent stake in the TNK-BP joint venture to Rosneft for $17.1 billion in cash and a 12.84 percent stake in Rosneft. Cleary M&A partners Russell Pollack and Daniel Braverman, antitrust partner Antoine Winckler, and finance partner Murat Akuyev are advising Rosneft on the deal, while Linklaters global corporate head Jeremy Parr, corporate partner Stephen Griffin, and litigation partner Michael Bennett are representing longtime client BP.

Cleary Gottlieb Steen & Hamilton, Linklaters, and Skadden, Arps, Slate, Meagher & Flom have landed lead roles advising various parties on a proposed $28 billion cash-and-stock deal that could see Russian government–backed Rosneft take control of the TNK–BP joint venture between British oil giant BP and four Russian oligarchs.

While not yet official, both BP and its Russian partners are reportedly close to a sale of their 50/50 stakes in TNK–BP, a transaction that would make Rosneft the world’s largest oil company and consolidate control of Russia’s natural resources in the hands of the Kremlin, according to The Moscow Times.

TNK–BP was formed through a $31.2 billion joint venture deal in 2003. Its existence over the past decade as the third-largest oil producer in Russia has been rife with international intrigue. Almost from the beginning, the alliance appeared to be a bad fit between London-based BP and the four Russian billionaires constituting the Alfa Group-Access Industries-Renova consortium (AAR) on the other side of the joint venture.

A 2008 dispute over control of the joint venture between BP and its Russian partners resulted in police raids on the Moscow offices of several firms caught up in the matter, which was resolved later that year when former TNK–BP president—and current BP CEO—Robert Dudley stepped down and left the country.

But lingering troubles remained. Last year BP and its lawyers from Linklaters sought to reach a $16 billion joint venture deal with Rosneft to explore for oil off of Russia’s vast Arctic coast. The accord enraged the four oligarchs behind AAR—Leonard Blavatnik, Mikhail Fridman, German Khan, and Viktor Vekselberg—who claimed that the arrangement violated a provision in the TNK–BP joint venture agreement giving them the right of first refusal to any other oil deals BP might pursue in Russia.

Skadden represented AAR before a three-member international arbitration tribunal in Stockholm that blocked BP’s Arctic joint venture with Rosneft in March 2011, according to our previous reports.

In the wake of the botched deal, black-clad members of Russia’s special forces raided BP’s Moscow offices in August 2011, ostensibly with the consent of a Siberian court where minority shareholders in TNK–BP are seeking billions in damages from BP. Eleven months later, in July 2012, the same arbitration court in the city of Tyumen ordered BP to pay $3 billion in damages to TNK–BP over the failed deal with Rosneft.

One of BP’s lawyers in that proceeding, Konstantin Lukoyanov, a senior attorney at Egorov Puginsky Afanasiev & Partners, a leading Russian firm known for its close ties to the Kremlin, excoriated the court’s ruling this summer.

“This court ruling seriously damages the Russian court system’s reputation and proves its inability to defend honest investors against illegal corporate attacks,” said Lukoyanov in a statement obtained by The Siberian Times.

With BP’s Arctic oil efforts temporarily spoiled, U.S. rival ExxonMobil and its lawyers from Skadden and Akin Gump Strauss Hauer & Feld stepped in and inked a $3.2 billion Arctic oil exploration deal with Rosneft in August 2011, according to our previous reports. The deal followed another $1 billion Black Sea oil exploration agreed to the previous January between Rosneft and ExxonMobil.

In June, BP announced that it would pursue a sale of its stake in TNK–BP. Rosneft formally informed BP in July of its interest in acquiring the British oil giant’s stake in the joint venture, according to a filing at the time by BP with the London Stock Exchange.

The Am Law Daily reported in September that Linklaters was advising longtime client BP as it sought a significant stake in Moscow-based Rosneft, 75 percent of which is owned by the Russian state. The deal is contingent upon BP selling its 50 percent stake in TNK–BP.

In the tentative deal now on the table, Rosneft is offering $28 billion in cash and shares to BP for its 50 percent stake in TNK–BP, according to a report Thursday by the Financial Times, which notes that in return BP would pick up a stake of 10–20 percent in Rosneft. By obtaining a significant stake in Rosneft, BP would effectively ensure its access to Russian oil revenues, which are expected to increase as the polar ice caps recede, exposing Arctic oil reserves.

Reuters reported Thursday that AAR might also sell its stake in TNK–BP to Rosneft. It remains unclear whether Rosneft has the money to consummate both acquisitions. Skadden has reprised its role advising AAR in the matter, according to British publication Legal Week, but the firm declined to comment when contacted by The Am Law Daily. (As one might expect, legal work for oligarchs can be quite profitable. Skadden, for instance, has reaped roughly $64 million in fees for representing Russian billionaire Roman Abramovich in a long-running dispute with exiled oligarch Boris Berezovsky.)

Igor Cheremikin, chief legal officer for AAR member Renova, serves as chairman of the board of directors for TNK–BP, whose general counsel is Igor Maidannik.

Legal Week reports that Cleary is advising Rosneft in the negotiations over its purchase of a stake in TNK–BP. The firm did not respond to a request for comment from The Am Law Daily about its role in the deal talks. (Larisa Kalanda serves as Rosneft’s vice president of legal support and is a deputy chair of the company’s management board.)

Cleary is no stranger to controversial Russian oil deals. The firm advised Russian state-backed Gazprom, the world’s largest gas company, on its $4.2 billion acquisition in 2009 of assets once owned by imprisoned Russian oil oligarch Mikhail Khodorkovsky, according to our previous reports. (Khodorkovsky, whose fate was featured in a Vanity Fair article earlier this year, remains in prison on charges many believe to be politically motivated.)

Cleary has been busy lately in the Russian market, advising privately owned commercial bank Promsvyazbank on its plans to pursue a $500 million initial public offering in London and Moscow, as well as representing the country’s largest lender, Sberbank, on a $5 billion sale of a 7.6 percent stake held by the Russian government last month. Legal Week reports that Cleary has also been tapped to advise Russian telecommunications giant MegaFon on its looming $2.5 billion IPO.

Freshfields Bruckhaus Deringer has also handled its share of work in Russia recently, advising the country’s state-owned railway operator JSC on its $1 billion acquisition of a transport and logistics business being sold by faltering French carmaker Peugeot Citroen, according to Legal Week.

A Freshfields spokesman declined to comment on whether the Magic Circle firm is also advising Rosneft on its TNK–BP initiatives, given its previous work for the company. (Freshfields advised Rosneft in September when it signed four new joint ventures with Norwegian rival Statoil to explore for oil in the Arctic and Pacific Oceans, according to U.K. publication The Lawyer.)

As for BP, which has been busy over the past two years selling off assets in an effort to raise capital to offset rising costs from a disastrous 2010 oil spill in the Gulf of Mexico, its in-house legal efforts are headed by group general counsel Rupert Bondy.

Earlier this month, the company tapped Kirkland & Ellis and Vinson & Elkins for counsel on the sale of a Texas refinery and other infrastructure assets in a deal that could be worth up to $2.5 billion. Gardere Wynne Sewell took the lead for BP in September on the $5.6 billion sale of some of its deepwater oil and gas assets in the Gulf of Mexico, and DLA Piper advised the company in August on the $2.5 billion sale of its refining and marketing business in Southern California.

DLA advised TNK–BP last year on a $1 billion oil exploration deal in Brazil, according to our previous reports.