BP has admitted that its ongoing battle to stem the flow of oil into the Gulf has so far cost it $930m (£638m).
The company said that its latest attempt to stop the massive leak is not guaranteed to succeed because of the difficult deepwater conditions in which the operation is being carried out.
Up to 1,300 workers are involved in the operation in a race against the clock to limit the environmental damage caused.
The company said in a statement: “The cost of the response to date amounts to about $930m, including the cost of the spill response, containment, relief well drilling, grants to the Gulf states, claims paid and federal costs. It is too early to quantify other potential costs and liabilities associated with the incident.”