BP has set aside a small dome designed to contain oil gushing from an underwater well in the Gulf of Mexico as it considers a new option for diverting the oil to the water's surface.

A BP representative told Reuters on Thursday that crews will deploy the dome "within the next couple of days" to capture the oil and direct it to a tanker on the water's surface through a series of riser pipes.

A pollution containment chamber, known as a 'top hat,' is loaded onto the deck of the motor vessel Gulf Protector at Wild Well Control Inc. in Port Fourchon, La., on Monday. (Patrick Kelley/Deepwater Horizon Unified Command/Associated Press)

Earlier, the London-based oil giant had said that it would first try sucking oil away from the gushing well with a tube that will be inserted into the jagged pipe leaking on the seafloor.

Company spokesman Bill Salvin said BP hopes to start moving the 15-centimetre tube into the leaking 53-centimetre pipe — known as the riser — on Thursday night.

But the multinational company has no time to waste.

BP announced Thursday it is spending $10 million US a day on cleanup costs and has spent $450 million since a drilling rig it had leased, the Deepwater Horizon, exploded on April 20 and sank about 80 kilometres off the coast of Louisiana.

The tab, based on a statement filed to the U.S. Securities and Exchange Commission, includes money it has given to the coastal states of Louisiana, Mississippi, Alabama and Florida and to the federal government for their response efforts.

The costs also include the company's attempts to contain the crude and ongoing work to drill a relief well.

'Top hat' approach

BP has not abandoned altogether plans for the dome, or "top hat," a smaller version of the 12-metre tall, 90-tonne box BP tried lowering over the well late last week. That box, shaped like a giant milk carton, had to be moved aside after a slushy mixture of gas and water clogged the opening in its roof.

The 'top hat' is lowered into the Gulf of Mexico in Port Fourchon, La., on Tuesday night. (Patrick Kelley/Deepwater Horizon Unified Command/Associated Press)Meanwhile, BP says it is increasingly hopeful that it will be able to stop the oil by plugging the blowout preventer, a 408-tonne piece of equipment that sits on top of the wellhead during drilling operations and whose valves can be closed remotely in case of an accident or increase in pressure.

BP is planning what it calls a "top kill" of the well: injecting materials "of varying densities and sizes" including golf balls, rubber and fibres into the preventer to clog it up before pumping heavy fluids into the well itself to prevent the flow of oil, the company said on its website.

More than 17.9 million litres of oil have flowed into the surrounding waters since the leaks were discovered on April 22.

"The systems are intended to be fail-safe; sadly and for reasons we do not yet understand, in this case, they were not," BP America president Lamar McKay testified Tuesday at a U.S. Senate committee hearing into the accident.

Hydraulic leak

Congressman Henry Waxman, who chairs the House energy and commerce committee, said Wednesday the committee's investigation into the oil spill revealed the blowout preventer had a leak in a crucial hydraulic system.

The well had also failed a negative pressure test just hours before the April 20 explosion, he said.

Video released Wednesday by BP shows the oil spewing from a yellowish, broken pipe 1,500 metres below the water's surface.

With files from The Associated Press