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(Corrects percentage fall in second paragraph)
LONDON, Feb 4 (Reuters) - BP, the West's no.4 oil company,reported weaker quarterly profits after its refining businessswung to a loss, and said it would increase the accountingprovision for the 2010 U.S. oil spill by $200 million.
The British company on Tuesday reported underlyingreplacement cost profit of $2.8 billion for the fourth quarterof 2013, 28 percent lower than the same period a year ago, butahead of a consensus forecast of $2.7 billion.
BP's lower profits are in step with what has been a torridearnings season across the "big oil" sector, which arestruggling to grow profits amid rising costs, the expense offinding fresh reserves and weak refining margins.
The world's largest publicly traded oil company by marketvalue, Exxon Mobil Corp, reported lower-than-expectedquarterly profit last week, while Chevron and BP's Europeanrival Shell both issued profit warnings in January.
BP, unlike its rivals, however, is also dealing with thefallout from the Gulf of Mexico oil spill which killed 11 menand despoiled the surrounding coastline in the United States'worst offshore environmental disaster.
BP said the provision to cover the spill's clean-up, fines,compensation and legal costs had risen to $42.7 billion from$42.5 billion last year.
BP said the fall in its earnings, which were hurt bydifficult conditions in its shrinking refining business andcosts associated with the start-up of its Whiting refinery inthe U.S., were partially offset by higher earnings from Rosneft.
Rosneft, the state-controlled Russian company intowhich BP folded its Russian business last year in exchange for a19.75 percent stake, delivered $1.1 billion of the profits. (Reporting by Sarah Young; editing by Kate Holton)
