Oil company BP, facing growing US government and public frustration and allegations of a coverup, says its engineers are working with government scientists to determine the real size of the Gulf of Mexico oil leak.
A month after rig leased by BP exploded, claiming 11 lives and unleashing the spill, sheets of heavy oil are starting to clog fragile marshlands on the fringes of the Mississippi Delta, damaging fishing grounds and wildlife.
Scientists fear parts of the huge fragmented slick will be taken to the Florida Keys and Cuba by ocean currents.
On Friday, BP said it captured 2,200 barrels (350,000 litres) of oil from the well in a 24-hour period on Thursday, down from the 5,000 barrels (795,000 litres) it said earlier.
Many scientists dismiss an original 5,000 barrel-per-day estimate of the total leaking oil as ridiculously low and say it could be as high as 70,000 barrels (11 million litres) per day or more.
BP denied any coverup and said some third-party estimates of the leak were inaccurate.
The oil company will attempt to choke off the well next week, perhaps on Tuesday, a company executive said on Friday.
The latest estimate by BP Chief Operating Officer Doug Suttles is a delay from the London-based energy giant's earlier estimate that it could proceed with the so-called "top kill" operation on Sunday.
President Barack Obama's administration is defending itself against accusations it has not done enough to deal with the massive oil spill in the Gulf of Mexico.
Speaking at a news conference, the White House spokesperson Robert Gibbs said they have put the utmost pressure on BP to do everything possible to stop the leak.
