BP stock struggled as the company's attempts to contain the oil spill was neared a potentially important stage on Friday.
The U.S. Coast Guard said the British energy giant plans next week to more than double its capacity for siphoning oil gushing from its ruptured deep-sea well, but a looming storm raised fears that the effort could be disrupted for days.
BP said it had paid out $2.35 billion so far in clean-up and compensation costs for the ecological disaster caused by the biggest oil spill in U.S. history. That does not include the $20 billion oil spill fund it has agreed to set up, nor the billions of dollars it will have to pay in fines.
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As the spill entered its 67th day, BP said two relief wells that offer the best hope of plugging its well were on track to intercept their target at a depth of 18,000 feet. The wells are due to be completed in August.
An April 20 explosion blew up an offshore rig, killing 11 workers, and blowing out the well a mile beneath the surface. The well has spewed millions of gallons of oil into the ocean, soiling the U.S. Gulf coastline and threatening multibillion dollar tourism and fishing industries.
Any slowdown in clean-up efforts could place more pressure on President Barack Obama, who has faced criticism over his handling of the crisis, and BP, which has seen $100 billion wiped off its market value since the start of the disaster.
In London, its stock plunged more than 6 percent on Friday, trading at its lowest levels since 1996, on talk it needs extra cash to fund the clean-up and worries about the bad weather.
Its U.S.-listed shares touched a new low for the second day and were down 4.77 percent in morning trading in New York.