Tropical Storm Alex has veered away from the Gulf of Mexico oil spill but experts warned that strong waves and winds could still upset efforts to halt the environmental disaster.

Coast Guard admiral Thad Allen sounded the alarm about the potential for a devastating impact the storm may have on efforts to contain and siphon off the oil in the Gulf.

"The weather is unpredictable and we could have a sudden last-minute change," he said.

He told reporters oil recovery operations would have to be suspended for two weeks if Alex were to hit the area.

National Hurricane Centre spokesman Dennis Feltgen said Alex would not directly threaten clean-up attempts.

"The storm is not an issue for the spill," he said.

The Miami-based centre showed the storm on a path toward hitting the coast of Belize later on Saturday (local time) and then moving across the Yucatan Peninsula, dumping rain across Central America.

Mr Feltgen said forecasters did not expect Alex to head into the north-east Gulf, "but that doesn't mean there won't be some wave impact."

"We are very pleased that there is no weather impact right now," said BP spokesman Ron Rybarczyk.

A two-week stoppage would exacerbate the spill that has defiled the Gulf coast's once pristine shorelines.

It would also mean the estimated 30,000 to 65,000 barrels of oil gushing from a ruptured wellhead down on the sea floor would be billowing crude and gas unchecked for days.

An estimated 1.9 to 3.5 million barrels have poured into the Gulf since the BP-leased Deepwater Horizon rig exploded on April 20.

Meanwhile, Shell Oil Co said about 300 non-essential workers from production platforms and drilling rigs in US-regulated areas of Gulf oilfields were being evacuated due to the forecast path of the tropical storm.

The Louisiana Offshore Oil Port (LOOP) - the US's only offshore oil port able to take more than one million barrels of crude from tankers - was operating normally yesterday.

"We're not doing anything differently, except watching it closely," said LOOP spokeswoman Barb Hestermann.

Exxon Mobil Corp and Chevron Corp said its Gulf operations were normal.

- AFP/Reuters