BP engineers have tried several different ways to stem the flow of the well, which is a mile under the surface. Millions of gallons of oil have poured into the Gulf of Mexico's waters since the rig blew up and sank April 20, killing 11 employees. 

The next option is called the lower-marine-riser package cap, in which an underwater robot uses a saw to cut the leaking pipe and put a cap over it. 

Suttles expects that procedure to capture most of the oil flow but he said it's not a "tight mechanical seal" that could take at least four days or longer. He called the option "complex" because humans can't assist at more than a mile under the ocean and "it has never been done before in this environment." 

"I'm confident the job will work but, obviously, I can't guarantee success at this time," said. 

BP is drilling two relief wells that could take up to two months to complete. The relief wells would allow BP to pour cement into the leaking well but Suttles said he hoped to have the leak plugged well before that. 

Cross-posted from E2-Wire.