BP's work on capping the Gulf of Mexico gusher was frozen Wednesday after the federal government raised concerns the operation could put damaging pressure on the busted well that could make the leak worse.
An administration official, who asked not to be identified because of the sensitivity of the talks with BP, said the government was acting out of "abundance of caution" and didn't want potentially dangerous pressure tests on a tighter containment cap that has been placed over the well to go ahead until BP answers questions about possible risks.
At the same time, BP on its own halted the drilling of two relief wells that are designed to be a more permanent solution to plug the well.
The delays were a stunning setback after the oil giant finally seemed to be on track following nearly three months of failed attempts to stop the spill, which has sullied beaches from Florida to Texas and decimated the multibillion dollar fishing industry.
The administration official said Energy Secretary Steven Chu, U.S. Geological Survey chief Marcia McNutt and other government scientists met with BP Tuesday in Houston and had a number of questions about the plan to test the integrity of the well. Chu and other officials want to ensure that putting downward pressure on the well will not cause further leaks, the official said.
"Our basic position was, if you can give us the answers we need ... then go ahead," the official said. Until then, "they can't go forward."
The official stressed that the government was acting out of "an abundance of caution" and still hopes the temporary cap can be placed on the well.
The new, temporary well cap had been seen as the best hope since April of stopping the geyser. Work on a permanent fix, relief wells that will plug the spill from below with mud and cement, also was halted.
Oil continued to spew nearly unimpeded into the water, with no clear timeline on when it would stop. BP shares were down 2.5 percent in afternoon trading in London after recouping some of their oil spill losses earlier this week, when the cap project seemed to be moving ahead.
"We want to move forward with this as soon as we are ready to do it," said Kent Wells, a BP senior vice president.
BP had zipped through weekend preparations for getting the 75-ton cap in place and undersea robots locked it smoothly into place Monday atop the well, raising hopes the gusher could be checked for the first time since the Deepwater Horizon rig leased by BP exploded April 20, killing 11 workers.
Wells said that it was the government's call late Tuesday to re-evaluate plans for testing the new cap, and that plans were on hold for at least 24 hours. Federal officials and the company will re-evaluate the best path forward after that time period.
The run-up to the now-delayed testing process was closely monitored from Washington. Allen, who came to BP's U.S. offices in Houston on Tuesday, also met with Chu and McNutt along with BP and industry representatives. President Obama has been receiving multiple daily briefings on the work's progress, his adviser David Axelrod said.
Wells did not commit with certainty to going forward with the testing, which would shut off the leak by closing valves on the cap and watching to see if it could hold the pressure from oil and gas in the well. Wells suggested other oil collection options might be redeployed.
Work on a permanent fix, a relief well that would plug the leak with heavy drilling mud and cement, was halted for up to 48 hours as a precaution because it's not yet clear what effect the testing of the new cap could have on it.
BP said on Tuesday that it halted work on a second relief well, but that holdup was expected. The company is drilling the second well as a backup in case the first doesn't work.
The relief well's timeframe has always been hazy, with company and federal officials giving estimates ranging from the end of July to the middle of August before it can be completed.
The surprise delay jarred Gulf Coast residents already weary of unending gloom.
On the Alabama coast, Joyce Nelson said every bit of news from the spill site increases her stress and sparks a new round of telephone calls between friends and relatives in Bayou La Batre, where the seafood industry is virtually shut down because of the spill. The slowdown at the rig site just made things worse.
"Everybody's calling everybody. It's hectic," said Nelson. "Everybody is worried about them blowing the whole thing out. If that happens, there's nothing they can do but let it drain out."
Roger N. Anderson, a marine geologist at Columbia University, said he believes BP and government scientists are just being very cautious and he's not worried.
Freezing work on the relief well may mean scientists are worried that clamping down the cap will push new pressure all the way down to the depths of the broken well, he said.
"So I wouldn't panic, is the answer. They're going to be very, very deliberate about this," Anderson said.
Assuming BP gets the green light to do the cap testing after the extra analysis is finished, engineers need to shut off lines already funneling some oil to ships to see how the cap handles the pressure of the crude coming up from the ground.
Finally, they would shut the openings in the 75-ton metal stack of pipes and valves gradually, one at a time, while watching pressure gauges to see if the cap would hold or if any new leaks erupted. The operation could last anywhere from six to 48 hours, once it gets started.
Scientists will be looking for high pressure readings of 8,000 to 9,000 pounds per square inch. Anything lower than 6,000 might indicate previously unidentified leaks in the well.
As of Wednesday, the 85th day of the disaster, between 92 million and 182 million gallons of oil had spewed into the Gulf.
BP underwater video: http://bit.ly/bwCXmR
Weber reported from Houston. Associated Press writers Matthew Daly in Washington, D.C., Colleen Long and Allen Breed in New Orleans and Jay Reeves in Bayou La Batre, Ala., contributed to this report.