BP is preparing to try to seal off its leaking well with a new cap that it says could for the first time in 12 weeks finally stop the flow of oil spewing into the Gulf of Mexico.
The energy giant has suffered numerous setbacks in its struggle to control the 85-day-old leak, which stands as the worst offshore oil spill in US history.
Watch the operation here
BP cautioned that tests of its latest containment system were not sure to succeed.
The potential breakthrough in efforts to fully contain BP's ruptured wellhead also came as the Obama administration issued a revised moratorium on deep-water oil drilling that critics called a mere repackaging of an earlier ban struck down by the courts.
The prospect of legal battles over the administration's bid to suspend deep-sea energy exploration in the Gulf already has had an effect on drilling, putting tens of thousands of jobs at risk, industry officials and analysts said.
The drilling moratorium and its toll on the oil and gas industry were expected to highlight the agenda today for a second day of hearings by President Barack Obama's independent oil spill commission, meeting in New Orleans.
Even as the seven-member panel began its investigation into the cause and effects of the spill, BP reported a potential turning point in the crisis.
Hours after starting up a new oil-siphoning system, BP said last night it had installed a 40-ton containment cap atop its leaking wellhead 1.6km underwater - a device larger and tighter-fitting than the one it removed on Friday.
Crude oil continued to pour into the sea for the time being, but BP said it planned to begin testing the new cap, and the internal pressure of the well, today by closing off valves on the device to constrict the flow of oil.
If the test goes as intended, it would mark the first time that the flow of oil from the crippled well has been halted, at least temporarily, since the 20 April explosion and blowout of the Deepwater Horizon drilling rig that killed 11 crewmen.
The test was expected to last six to 48 hours, during which time two smaller siphoning systems, including the one brought online yesterday, will be turned off. But BP warned the outcome was uncertain.
