Progress made on Deepwater Horizon

"In a perfect world with no interruptions, it's possible to be ready to stop the well between July 20 and July 27," said the head of BP's Gulf Coast restoration unit, managing director Bob Dudley, in an interview. He added that this "perfect case" is threatened by the hurricane season and is "unlikely."

Weather will be an ongoing concern, Allen said. In addition to slowing the connection of the Helix, Allen said, it is a factor in deciding whether to remove the ill-fitting cap now being used to feed oil to the Discoverer Enterprise and replace it with a tighter-fitting version.

Unlike the current cap, the tighter cap presumably would not allow oil to escape. But Allen said officials have still not decided whether they want to remove the current cap because thousands of barrels of oil that otherwise would have been captured would escape into the sea while the caps are being changed. It would take days to replace the cap under ideal weather conditions. The length of time would be extended in the event that severe weather caused an operational shutdown.

"We are still reviewing the technical specifications that were provided to us by BP, the procedures that would be done, the amount of time it would take and the weather window," Allen said. "We are talking about that inside the administration right now and those talks are continuing."