Rosneft is poised to secure a tighter grip on Russia's oil industry with a bid for BP's 50 per cent stake in TNKBP, the third largest producing company in the world's top oil exporting nation. Sources familiar with the actions of BP, Ros-neft, their advisers and financiers said a bid had been submitted to BP that valued the whole of TNK-BP at over $50 billion and BP's half at more than $25 billion. Rosneft has offered to buy BP's partners in the venture, the AAR consortium owned by four Soviet-born tycoons, according to sources in London and Moscow.