British energy giant BP said on Friday that its response costs linked to the huge Gulf of Mexico oil spill have risen to about 930 million dollars (753 million euros).
"The cost of the response to date amounts to about 930 million dollars, including the cost of the spill response, containment, relief well drilling, grants to the Gulf states, claims paid and federal costs," BP said in a statement.
"It is too early to quantify other potential costs and liabilities associated with the incident," it added.
BP's market value has dropped by billions of dollars since the Deepwater Horizon oil rig, operated by BP and owned by US contractor Transocean, sank on April 22 -- two days after a massive explosion killed 11 workers.
BP was meanwhile pressing on with a risky bid to plug the ruptured oil well, which it said was going as planned, while new data showed the huge Gulf of Mexico slick is now the worst spill in US history.
"Operations on the top kill procedure continue," BP said in Friday's statement.
Amid a looming environmental catastrophe, there were also growing fears for the health of cleanup workers, some of whom had to be airlifted for treatment after falling sick while out at sea.
Even if BP's "top kill" maneuver succeeds in capping the leak, millions of gallons of crude are sloshing about in the Gulf waters and a visibly angered President Barack Obama moved to clamp down on the oil industry.
"If nothing else, this disaster should serve as a wake-up call," Obama said Thursday at his first formal White House press conference in 10 months, called specifically to address the crisis.
"My job is to get this fixed," Obama said, a day before his second trip to the Gulf of Mexico to oversee disaster relief efforts.
"In case you were wondering who's responsible, I take responsibility."
BP said it had paused the "top kill" for some 16 hours on Thursday to monitor the results, before resuming it again as night fell.
US government scientists released data showing the oil may have been flowing from the burst pipe at a rate up to four times higher than previous estimates by BP and the federal government.
The new estimates put the flow at 12,000 to 19,000 barrels (504,000 to 798,000 gallons) a day -- much higher than the previous estimate of 5,000 barrels.
That would mean between 18.6 million gallons and 29.5 million gallons of oil have seeped into the Gulf -- far more than the roughly 11 million gallons of crude spilled in the 1989 Exxon Valdez disaster off Alaska.
With 100 miles (160 kilometers) of Louisiana coastline already contaminated, there are fears US officials may order the burning of the state's unique marshlands, home to a variety of endangered birds and mammals.
Obama dismissed charges the government response had been too slow but said it was legitimate to question whether BP was "being fully forthcoming about the extent of the damage."