Rosneft was due Thursday to become the world's largest publicly traded oil company when it strikes a deal for BP's stake in the British giant's troubled TNK-BP joint venture believed to be worth nearly $30 billion.
The government-owned Russian oil leader needed to wait until a 0800 GMT deadline to expire before making a formal proposal for BP's half in TNK-BP during talks in London between company chief Igor Sechin and the British group's executives.
The Financial Times reported that the cash-and-shares deal would be worth $28 billion and see BP grab a stake of between 10 and 20 percent in Rosneft -- up significantly on its current 1.4 percent holding in the giant.
Rosneft and the four Russian billionaires who own the other half of TNK-BP had signed a memorandum of understanding on Tuesday that would see the state firm acquire the tycoon's half at a later date.
The billionaires have experienced strained ties with the Russian government and were forced to concede that a company run by them and Rosneft jointly would most likely fail to function and require them to eventually sell their stake.
Various reports put the value of the deal with the tycoons -- to be most likely completed after the BP swap is set in place -- at $28-$29 billion.
The Financial Times said the BP board will consider Rosneft's Thursday offer on Friday.
The expected deal will make Rosneft into the world's biggest publicly traded oil producer with daily crude output of more than three million barrels a day -- far more than current leader ExxonMobil's 2.3 million barrel figure.