Crews working on a huge oil spill were evacuated yesterday as a tropical storm barrelled towards the Gulf of Mexico, prolonging the region's environmental and economic nightmare.

The cap in place for a week on the ruptured well will remain in place, but efforts to complete relief wells for a permanent fix were set back by the evacuation as Tropical Storm Bonnie churned towards the area.

BP said in a statement yesterday it suspended work on its relief well drilling in consultation with government officials "because of potentially adverse weather" associated with Bonnie.

At 1200 GMT, Bonnie was some 130 kilometres south-east of Miami, Florida, packing sustained winds of 65 kilometres per hour.

The storm was moving at a fast clip of 31 kilometres per hour towards the Florida Straits and the Gulf of Mexico, the National Weather Service said.

Tropical storm warnings were posted for much of the Florida coast and storm watches were posted for areas as far west as Morgan City, Louisiana.

Bonnie was expected to move over southern Florida late yesterday, reaching the eastern Gulf of Mexico today - and arrive at Louisiana tomorrow.

Louisiana Governor Bobby Jindal issued an emergency declaration which will help speed state assistance to areas in need.

US spill response chief Admiral Thad Allen announced last Thursday that the nearly 2,000 people responding to the BP oil spill at the well site would return to land "due to the risk that Tropical Storm Bonnie poses."

Allen has previously said evacuating crew could delay an operation to finally plug the runaway well by up to 12 days, but he said last Thursday safety concerns would trump the desire for a speedy resolution.

"While these actions may delay the effort to kill the well for several days, the safety of the individuals at the well site is our highest concern," he said.