New Orleans, Louisiana - The United States government sent BP a $69-million bill for the Gulf of Mexico oil spill on Thursday, warning it was only the first invoice, as undersea robots poised to try to curb the leak.
"The federal government will, at some point today, send what I would call a bill for 69 million dollars of expenses incurred up to this point to BP," White House spokesperson Robert Gibbs said.
He said the bill was to reimburse American taxpayers for the government's costs so far in battling the worst oil spill in US history, with thousands of barrels of oil pouring into the Gulf every day.
Thousands of people have been deployed to the southern states to try to contain the spill, and clean up the slick as it washes ashore, and President Barack Obama was preparing to make his third trip to the region on Friday.
Speculation is also growing that the disaster will prompt the president to call off a scheduled visit to Indonesia and Australia for the second time, after an original journey was put off during the push for health care reform.
In a ray of good news, BP engineers managed to slice off the rig's fractured riser pipe with a pair of giant shears and were preparing on Thursday to cover the jagged hole with a cap topped with a syphon and linked to a surface ship.
"We have cleared the riser from the top of the wellhead, and the team is currently working to complete the cleanup operation before we put the cap onto top of the well," under-fire BP chief executive Tony Hayward said.
"It's an important milestone," he added.
But he warned it could take 12 to 24 hours after the cap is put in place to know if it is managing to contain the worst of the spill, amid warnings that now the broken pipe has been cut off, the oil flow will increase initially.
"In some senses... it's just the beginning. It's been an extraordinary endeavour on the part of many, many people," Hayward said.
BP has battled unsuccessfully to cap or contain the disastrous leak since an April 20 explosion tore through the BP-leased Deepwater Horizon rig just off the Louisiana coast.
Hayward acknowledged earlier in an interview with the Financial Times that the British energy giant had been unprepared for the disaster and "did not have the tools you would want in your tool kit".
The US government has estimated the flow of oil before the riser was cut away at 12 000 to 19 000 barrels a day.
BP's operation to drill two relief wells - seen as the only way to permanently cap the failed wellhead - is on target to be completed in mid-August, US officials said.
The slick, floating along in a myriad of oily ribbons, is now threatening Alabama, Mississippi and Florida after contaminating more than 200km of Louisiana coastline.
With the slick expected to arrive within days in the Florida panhandle, Coast Guard investigators were probing unconfirmed reports that tar balls and an oily substance had been found in the famed Florida Keys.
Meanwhile, Admiral Thad Allen, who is co-ordinating the government's response to the spill, said nearly one million gallons of dispersants have been used to break up the oil in the Gulf.
"We're approaching the million gallon mark and it's a milestone and there are concerns about that and we will continue to work the dispersants very, very closely."
Many environmentalists have voiced concern over the unprecedented use of so much dispersant, warning its long-term effect on wildlife - already threatened by the huge oil spill - is unknown.
A University of Miami study showed the oil slick's surface area now stretches across more than 24 000 square kilometres of the Gulf - triple the size of satellite imagery from May 1.
Experts also warn the majority of the oil is contained in vast underwater plumes that cannot be measured from above.
US officials have closed more than a third of Gulf of Mexico waters, extending a fishing ban to about 37 percent of the Gulf's federal waters. - AFP