Oil majors BP and Rosneft have signed a long-term contract which will see the British group pay at least $1.5bn upfront for the supply of oil from the Russian company.The five-year agreement, which is on a pre-paid basis, covers export deliveries of up to 12m tonnes of oil products which can be replaced by oil.Supplies should start in July, Rosneft said on Friday.The signing is the second major agreement between the two companies since Rosneft's Executive Chairman Igor Sechin had a visa ban and asset freeze imposed on him. Sechin, a close ally to Russian President Vladimr Putin, was hit with sanctions from the West, along with a number of others in Putin's inner circle, after the annexation of Crimea from Ukraine earlier in the year. Rosneft itself has not been affected by these sanctions. Last month, BP and Rosneft agreed to jointly explore for tight oil in Russia.Friday's deal, according to Sechin, "opens up new opportunities" for both BP and Rosneft."It provides BP with stable supply chain and guaranteed quality of oil products and allows Rosneft to support high profitability of its sales activities and acquire additional financial resources in accordance with the referential nature of such deals," he said in a statement.BC