BP has said efforts to seal off the ruptured oil well spewing crude into the Gulf of Mexico could take three months.
The oil giant has begun work on a relief well to intercept the leaking well and permanently seal it but this could take “some three months”, the firm said.
An estimated 1.6m gallons of oil are estimated to have spilled since the BP-operated Deepwater Horizon rig exploded and sank on April 20, killing 11 workers.
A huge slick is now threatening the coast of Louisiana with US President Barack Obama warning of a “potentially unprecedented environmental disaster”.
The drilling of the relief well, which is planned to meet the existing well around 13,000 feet below the seabed, was a “key step” in tackling the crisis, BP chief executive Tony Hayward said.