Workers have begun putting a giant concrete-and-steel box over the blown-out oil well at the bottom of the sea in an untested bid to capture gushing crude and avert a wider environmental disaster.
The 100-tonne containment vessel is designed to collect as much as 85pc of the oil spewing into the Gulf of Mexico and funnel it up to a tanker. It could take several hours to lower it into place, after which a steel pipe will be installed between the box and the tanker.
The whole structure could be operating by Sunday.
"We haven't done this before," said BP spokesman David Nicholas. "It's very complex and we can't guarantee it."
The mission took on added urgency as oil started washing up on delicate barrier islands.
Dangerous fumes rising from the oily water on a windless night had delayed the lowering of the box for hours. The fear was that a spark caused by the scrape of metal on metal could cause a fire.
The technology has been used a few times in shallow waters, but never at such extreme depths -- 5,000ft down, where the water pressure is enough to crush a submarine.
The box -- which looks like a peaked, 40ft-high outhouse, especially on the inside, with its rough timber framing -- must be accurately positioned over the well, or it could damage the leaking pipe and make the problem worse.
Mr Suttles said he is not concerned about that happening. Underwater robots have been clearing debris near where the box will be placed to avoid complications.