Thad Allen, the retired coast guard admiral who is overseeing the US government's response to the oil spill, said that uncapping the well and calling ships back to shore is "necessarily going to be a judgement call".

Allen was watching the weather on Thursday to see how the storm developed before making a decision on the future of the clean-up effort.

No decisions

Scott Dean, a spokesman for BP said on Thursday that no decisions on uncapping the well or removing clean-up ships have been made. 

in depth

BP placed a temporary plug called a storm packer deep inside the well tunnel, in case it had to be abandoned until the storm passes.

"What we didn't want to do is be in the middle of an operation and potentially put the relief well at some risk," Kent Wells, BP's vice-president, said.

Transocean Ltd., the company which operates the rig drilling relief wells, has been watching the storm but had not planned evacuations on Thursday.

"Obviously as storm tracks toward the rig we'd have to take initial actions, pulling up subsea equipment, securing the location and preparing to move out of the way," Guy cantell, a company spokesman, said. 

Scientists have been watching under-water video and well-pressure data for days, trying to determine if the capped well is holding tight or in danger of rupturing and causing an even bigger disaster.

BP's oil rig exploded on April 20 and experts believe that 35,000-60,000 barrels of oil poured into the Gulf of Mexico every day for about 13 weeks, threatening vulnerable wildlife and destroying local economies and communities.

The well cap, which was sealed in mid-July, is designed to stop the spill until BP  August.