A drill rig headed back to the site of the Gulf of Mexico oil spill yesterday after an oncoming storm weakened, as officials raced to restart work to permanently 'kill' the leaking well.

The Development Driller 3, assigned to drill a relief well that will help finally seal the ruptured well, had been evacuated from the area as Tropical Storm Bonnie headed for the region.

But the storm system had weakened to a tropical depression by yesterday, allowing the drill rig to turn around.

"The Development Driller 3 (DD3) is on its way back," BP spokesman Bryan Ferguson told AFP. "It's the one that's drilling the first relief well and it's the most critical one and it is turned around and is headed back right now."

Officials are eager to return to work on operations that should finally seal the leaking well, months after the April 20 explosion aboard the BP-leased Deepwater Horizon oil platform, which killed 11 workers and sunk the rig.

A cap over the wellhead has shut in leaking oil since July 15, but final operations to seal the well for good were halted when forecasters announced storms were headed to Gulf.

Retired Coast Guard Admiral Thad Allen, the US official overseeing the spill response, had said an evacuation could set back efforts to finally 'kill' the leaking well by up to 12 days.

But the storm system weakened as it crossed Florida moving west from the Caribbean, and several ships, including some operating underwater surveillance robots, had not even left the site by the time the DD3 began heading back.

Ferguson said it would take around 21 hours to reconnect the DD3 to drilling operations some 152 metres beneath the sea surface, after which a decision would be made on whether to restart drilling. The rig is drilling the first of two relief wells that will be used to definitively plug the devastating spill.

BP and US officials currently plan two operations to kill the well.

The first, a 'static kill', involves pumping heavy drilling fluids known as mud through the blowout preventer valve system that sits on top of the well, and then injecting cement to seal it.

The process is similar to a "top kill" attempt that failed, but officials say the cap placed over the leak will made the operation easier and more likely to succeed.

However, BP and US responders have said the ultimate solution to the leak will be via a relief well, which will intersect the original well.

Using the same process as the static kill, drilling fluid, which is denser than oil, will be pumped via the relief well until the flow of crude is overcome, allowing the damaged well to be sealed with cement.

Gulf residents facing economic and environmental disaster as a result of the spill, which has now washed up on the shores of all five states in the region, are desperate to see the well sealed for good.