BP will start replacing the cap over the blown-out oil well in the Gulf of Mexico over the weekend, reports say.
It is hoped the new cap will significantly increase the amount of oil being captured from the sea-bed.
However while it is being replaced oil will flow unimpeded into the sea.
BP’s submersible robots could start removing the current containment cap from the ocean floor as early as Saturday, the Coast Guard commander overseeing the response said.
Admiral Thad Allen said the flow of leaking oil could be shut off by Monday. But in that time hundreds of thousands of barrels of oil could flow unabated into the ocean.
“We have a significant chance to dramatically reduce the oil that’s being released into the environment and maybe shut the well in altogether in the next week,” he said.
“I use the word ‘contained’,” said Admiral Allen. “‘Stop’ is when we put the plug in down below.”
BP is continuing work on what it hopes will be the ultimate solution – drilling two wells to intercept and block the leak, under the seabed.
Lull in storms
BP is hopeful the new cap will enable it to capture almost all the escaping crude, says BBC correspondent Madeleine Morris in Washington.
At the moment it is believed that BP is siphoning off only around half the leaking oil.
Current US government estimates of the spill range from between 35,000 to 60,000 barrels a day.
The company is taking advantage of a predicted week-long lull in the storm season to make the changes to its operation.
It also plans to connect a third containment ship to capture more oil.
On Thursday BP said its operation to drill a new relief well to stop the Deepwater Horizon leak was ahead of schedule.
The latest efforts to halt the environmental catastrophe come as one of BP’s partners in the deepwater well refuses to pay its share of the costs so far.
Houston-based Anadarko, which owns 25% of the Macondo well, was asked to pay $272m (