As many as 40,000 barrels (1.7m gallons) of oil a day may have been gushing out from a blown-out Gulf of Mexico well, doubling many estimates.
The US Geological Survey says that flow rate could have been reached before a cap was put on the well on 3 June.
BP's chairman has been asked to meet Barack Obama next week, amid assurances from the UK and US that bilateral ties will not be affected by the crisis. UK PM David Cameron and President Obama will discuss the spill at the weekend.
Oil has been leaking into the Gulf since the Deepwater Horizon rig exploded on 20 April and sank off the coast of the US state of Louisiana, killing 11 workers.
BP said the device placed on the well collected 15,800 barrels of oil on Wednesday - slightly up on the 15,010 barrels collected in the previous 24-hour period.