BP said today it was making progress on what could prove its most effective effort yet to contain the Gulf of Mexico oil leak, but warned that the verdict could be several days away.
A new cap being placed on top of the gusher is intended to provide a tight seal and might eventually allow the oil giant to capture all crude leaking from the well for the first time since an April 20 Deepwater Horizon oil rig explosion set off the environmental crisis.
But several previous failed attempts to stop the leak have made BP careful to keep expectations grounded.
"We're pleased with our progress," said BP senior vice president Kent Wells, who then hastened to add the operation was still expected to last up to six more days.
Asked during a conference call if the new cap and collection efforts would end the spilling of oil into the Gulf, Mr Wells said only that BP would capture all the oil "at some point."
He said BP may have to bring another vessel back online and add additional collection capacity in order to stop the oil flow altogether.
Officials will not be satisfied the cap is working until they have run tests on whether it can withstand the tremendous pressure of oil pushing up from below the seafloor, Mr Wells said.
"We've tried to work out as many of the bugs as we can. The challenge will come with something unexpected," he said.
The leak has been gushing largely unchecked since an old, leaky cap was removed from the wellhead on Saturday to make way for the new one.
Between 88 and 174 million gallons have already spilled into the Gulf, according to US government estimates.
Wary Gulf residents and officials reserved judgment about BP's latest effort and said the damage already done to the environment, fishing and tourism would haunt the region for a long time either way.
"At this point, there have been so many ups and downs, disappointments, that everybody down here is like, 'We'll believe it when we see it,"' said Keith Kennedy, a charter boat captain in Venice, Louisiana.
Robotic submarines finished removing a broken piece of pipe that was bolted around the leak at around 3am yesterday. That paved the way for the installation of a pipe-like connector called a flange spool that will sit on top of the spewing well bore.
The new cap would be mounted on top of that connector and have flexible pipes leading up to surface ships.
The work was being closely monitored at the White House, where President Barack Obama was being briefed several times a day, adviser David Axelrod said.
"We have every reason to believe that this will work," he said.
The new cap will be aided in containing the leak by the arrival of the Helix Producer, a vessel that will be able to take in about one million gallons of crude a day by tomorrow after gradually building up. The Helix connected to flexible pipes from the well Friday, and crews have been running tests since then.
Like another vessel already operating, the Q4000, the Helix will take in oil through connections beneath the new seal. Once the new cap is affixed, two other vessels are to connect to it for their oil collection.
But the hurricane season that lasts through November could interfere. There are no storms forecast now, but if one blows through, the ships collecting the oil may have to leave and crude would spew again for days into the water.
Relief wells are being dug for the permanent fix, a "bottom kill" in which heavy drilling mud and cement are pumped in from below the broken wellhead.
Meanwhile tens of thousands of people sang and danced on an Alabama beach at a free Jimmy Buffett concert meant to help the Gulf Coast through the oil spill crisis.
The show at Gulf Shores accomplished its goal of luring visitors with car parks fuller than they had been in days outside hotels, condominiums, restaurants and souvenir shops.