BP is testing a technique known as "top kill" that involves injecting heavy liquids into the well, but Mr Wells said: "We have to be careful in terms of setting expectations."  A pipe is already siphoning around 2,000 barrels to the surface, but BP will attempt to seal the leak entirely using "top kill" in the coming days.  With the company facing unprecedented hostility from the US public and politicians, its chairman Carl-Henric Svanberg broke his silence to insist that BP remains important to America. In a newspaper interview, he said: "The US is a big and important market for BP, and BP is also a big and important company for the US, with its contribution to drilling and oil and gas production. So the position goes both ways,"  BP meanwhile briefed US officials on its preliminary inquiry into the fatal accident, saying it should have been prevented by one of seven different mechanisms.  The Deepwater Horizon rig, owned and operated by BP's contractor Transocean, exploded and sank killing 11 men a month ago. Halliburton, an oil services company, had worked on the rig's well cementing just before the accident.  BP's report is focusing on seven areas of safety that appear not to have functioned properly. It found:  • The well should have been properly sealed with cement and covered in a casing to withstand a build-up of pressure.  • There ought to have been thorough testing to halt a build-up of pressure and procedures should have detected hydrocarbons surging up the well.  • The rig's safety valve, known as a blowout preventer, should have shut off the well at the push of a button from multiple locations on the rig.  • The preventer should have shut automatically if connection was lost with the rig, and been receptive to robots closing it manually.  None of these measures was able to stop it from spilling 4m gallons that is threatening wildlife off the coast of Louisiana and has already killed 300 birds.
BP has found that multiple failings in safety processes and equipment on the    Deepwater Horizon rig caused its giant oil spill in the Gulf of Mexico.