Russian state oil company Rosneft closed a historic deal to buy TNK-BP from UK-based BP and four tycoons, releasing $40 billion cash to the sellers and becoming a bigger oil producer than Exxon Mobil, the world’s No.1 investor-owned company.

TNK-BP was created in 2003 by a merger of BP’s Russian operations with those of the Alfa-Access-Renova (AAR) consortium of four Soviet-born billionaires.

The $55 billion deal, which also gives BP a near 20 percent stake in Rosneft, was announced last year after months of on-off negotiations. It is the biggest in Russia's corporate history.

It tightens the government's grip on the energy sector and is a victory for Rosneft chief Igor Sechin, a close confidant of Russian President Vladimir Putin, creating a business with annual production of about 4.6 million barrels of oil equivalent, more than Exxon Mobil, the world's No.1 investor-owned company.

The deal gives Rosneft an expert international shareholder and extra oil output revenue it can put to work to explore Russia's vast reserves and to replace ageing and depleting fields. It hopes to extract $10 billion a year of costs savings.

BP, selling one half of the business, gets some hard cash in the bank that reduces its dependence on an uncertain future in the country. It has promised some of the $12.3 billion to shareholders, and can set the rest against its multibillion dollar Gulf of Mexico oil spill liabilities.

Cash also goes to the private businessmen who owned the other half of TNK-BP to fund their international ambitions.

A BP spokesman confirmed that the company's cash was in the bank, and outside Russia. BP has made huge profits in its 20-year history there, but where increasing state involvement has hampered its business plans over the past decade.

TNK-BP was created in 2003 by a merger of BP's Russian operations with those of the Alfa-Access-Renova (AAR) consortium of four Soviet-born billionaires, some of whom will stay in the oil industry by setting up international investment business.

Thursday's deal has brought the state share in Russia's oil sector, the world's largest by output, to more than 50 percent. It has drawn criticism from some analysts and managers of non-state enterprises, who said it would hinder competition and production growth.

The acquisition closed three months ahead of its June 30 deadline, as predicted in an exclusive Reuters story of Feb. 22.

"This is a historic day for BP in Russia," BP Chief Executive Robert Dudley said in a statement. "BP has invested in Russia for more than 20 years and for a decade we have been Russia's largest foreign investor through our involvement with TNK-BP."

Dudley finalised the massive and complex cash and stock transfers in an all-night round-table session with Rosneft Chief Executive Igor Sechin, Russian President Vladimir Putin, attendant lawyers, and bankers from Bank of America Merrill Lynch and CitiGroup, at Putin's official residence in Moscow.

Both Dudley and Sechin were in London for a news conference on Thursday evening at which Sechin, a close Putin confidant and former deputy prime minister, said BP would be "welcome" to join exploration projects with his invigorated company.

"The pot is so enormous that we would welcome BP at one of our larger projects," he said. "We already know what they would prefer to develop and in the near future we will find the one."

He said BP would get no special treatment over rivals like Exxon, Statoil and ENI, which have already signed up to work in the Arctic on some of Rosnefts 41 offshore licences, although both he and Dudley pointed out that BP would benefit anyway as a one-fifth Rosneft shareholder.

Dudley, under huge pressure in recent months as the deal came together during ongoing oil spill litigation in the United States, looked more relaxed than he did a few weeks ago at the company's fourth quarter results presentation.

To acquire TNK-BP, which pumps oil at the rate of around 1.5 million barrels per day, Rosneft had to borrow up to $40 billion, mostly from Western banks. It has managed to cover its most immediate needs by lining up a syndicated loan as well as $10 billion in financing from traders Vitol and Glencore .

According to industry sources, Rosneft has been in talks with China to secure cheaper loans in exchange for boosting oil supply to the world's top energy consumer.

Rosneft paid $27.73 billion cash to AAR for its half of Russia's third-largest crude producer.

The deal with BP nets the British company $12.48 billion in cash, including a $700 million dividend paid out in December after the deal was struck, plus an 18.5 percent Rosneft stake that lifts its holding in the state firm to 19.75 percent.

BP will have two seats on the Rosneft board, including one offered to Dudley, who served as chief executive of TNK-BP until 2008.

The AAR part of the deal will share the cash pot between Mikhail Fridman, German Khan, Viktor Vekselberg and Len Blavatnik, all of whom emerged as tycoons after the Russian privatisations of the 1990s.

Khan, who effectively heads TNK-BP and is Fridman's partner in the Alfa Group consortium, sought advice and broached potential partnerships.

"Alfa Group is currently setting up a major, new international investment business which draws on the group's significant expertise in oil and gas and telecoms, looking for long-term, strategic investment opportunities in Russia, North and South America, Asia and Africa," Stan Polovets, the CEO of AAR, told Reuters.

He added that the new company will receive a significant part of the proceeds from the sale of TNK-BP, of which Alfa Group's share is close to $14 billion.

Sources have told Reuters that mining tycoon Vekselberg of the Renova Group and Blavatnik of Access Industries, are likely to bow out and focus on other ventures and charity work.

One of the holding companies in TNK-BP's structure is based in Cyprus. Sechin said the bank closures there of recent days as a financial crisis rages did not result in any losses for any parties involved.-Reuters