The storm threatening the Gulf of Mexico oil spill has intensified and decisions will be made later Thursday on whether to evacuate staff and remove the cap sealing the well, the White House said.

"Right now, we have a trajectory that puts it into the Gulf," said White House spokesman Robert Gibbs. "I think there's no doubt that this storm has intensified, and decisions will be made probably likely later this afternoon on moving some of that equipment out."

"If the area is evacuated, whether to keep the sealing cap on is a decision that will be made over the next several hours."

Storm warnings were extended Thursday from the Caribbean around the Florida Keys to the Gulf Coast, but there was no immediate order from BP or the US government to suspend operations and pull hundreds of staff back to shore.

With no crews on site to monitor pressure inside the well, top US official Admiral Thad Allen has suggested the cap that has prevented crude from entering the sea for the past week may have to be opened up again or even removed.

An evacuation is expected to delay by up to two weeks the final operation to plug BP's runaway well, which has unleashed millions of barrels of crude on Gulf Coast shorelines in one of America's worst ever environmental disasters.