Hundreds of miles of booms are being laid along the coastline
BP officials desperate to stem a huge oil spill in the Gulf of Mexico will try to place a smaller dome over the blown-out well, it is reported.
The so-called top hat dome could be in place within 72 hours, chief executive Tony Hayward said.
The latest bid to plug the gushing well comes after previous attempts to stem the flow failed.
A growing slick from the BP-leased rig is threatening an environmental disaster along US coasts.
The top hat dome could be in place within 72 hours, Mr Hayward told a press conference in Houston, Texas, on Monday.
Kent Wells, senior vice president in BP's exploration and production business, was quoted as saying that the operation would be an unprecedented challenge.
The latest attempt to halt the leak comes after the failure of attempts to lower a 98-tonne concrete-and-steel funnel 5,000ft (1,500m) to the seabed.
It had been BP's best hope to contain the main leak while it tried to stop it altogether by drilling relief wells nearby.
But a build-up of gas hydrates - crystalline water-based solids resembling ice - inside the device blocked the exit at the top, and it had to be put aside until engineers could decide what to do.
BP experts believe a smaller box, dubbed the "top hat," might not suffer the same clogging problem.
There are fears that it will be less effective in capturing the leaking oil. But it could be operating within 72 hours.
'We'll keep trying'
The oil giant is also considering a plan to inject a so-called "junk shot" of debris made up of golf balls and shredded tyres, it was revealed.
"I can't tell you if any one of them will work but as long as we have options we're going to keep trying," BP Chief Operating Officer Doug Suttles said on NBC.
"The goal here has to be to get the flow stopped."
Some 5,000 barrels (210,000 gallons) of oil a day are flowing into the sea.
Mr Suttles said it may be possible to stem the flow by blocking the well's failed blowout preventer.
"We have some pipe work on the blowout preventer, and if we can open certain valves on that we could inject basically just rubber and other type of material into [it] to plug it up, not much different to the way you might plug up a toilet," he said.
Admiral Thad Allen of the US Coast Guard said it could plug the main leak.
"They're going to take a bunch of debris, shredded up tyres, golf balls and things like that, and under very high pressure shoot it into the preventer itself and see if they can clog it up and stop the leak," he told CBS television.
ATTEMPTS TO CONTROL SLICK
Booms have been partly successful although rough seas have washed oil over them
Some controlled burning of oil has taken place, but it causes serious air pollution
About 325,000 gallons of dispersant have been used, although scientists warn it may kill marine life
A relief well is being drilled but could take many weeks
A huge steel funnel suffered a build-up of ice-like crystals and had to be put aside
However, experts have warned that any further damage to the blowout preventer - a huge valve system meant to turn the oil off - could see it shooting out at 12 times the current rate.
In other developments, a BP official told the Associated Press news agency on Monday that the company had received US government approval to continuously pump dispersant chemicals underwater.
BP spokesman Mark Proegler said engineers began pumping dispersant on the site on Monday morning.
Thousands of gallons of dispersant have been dropped over oil on the surface, but have not been tried at such depths before.
Scientists and fishermen have expressed concern that the chemicals could kill marine life.
BP revealed on Monday that the oil spill had cost the company $350m (£233m) so far.
It did not speculate on the final bill, which many analysts expect to run into tens of billions of dollars.
The Deepwater Horizon rig caught fire and sank following an explosion last month.
The resulting slick has so far thwarted all efforts by BP and US officials to bring it under control.
Mr Suttles said another option being discussed to stem the flow was to tap into the broken riser pipe and take the oil directly.
The broken pipe is almost a mile (1.6 km) down on the ocean floor with little visibility for engineers using remotely controlled vehicles.
Although the Deepwater Horizon was operated by Transocean, BP is responsible for the clean-up.
Wildlife in the Gulf of Mexico is already suffering
The slick has so far covered about 2,000 sq miles (5,200 sq km).
US President Barack Obama is due to meet senior officials at the White House on Monday to review BP's efforts.
A sheen from the edge of the slick is surrounding island nature reserves off Louisiana and tar balls have reached as far as the Alabama coast.
The low-lying region contains vital spawning grounds for fish, shrimp and crabs and is an important migratory stop for many species of rare birds.
Louisiana's fishing industry has ground to a halt in certain areas due to health concerns about polluted fish.
Booms and bundles of absorbent material have been laid along shorelines to try to protect them.
Teams are also filling sandbags which the Louisiana National Guard will airlift on Monday to five spots along a threatened stretch of coastline.
The first two oiled birds rescued from the spill have been cleaned and were due to be released back into the wild later in the day.
The birds - a gannet and a pelican - were to be freed at Pelican Island National Wildlife Refuge in Florida.