BP and the US coast guard sent oil-skimming ships back to shore due to rough seas, which are likely to last for days.

Officials also had to remove barges that had been blocking oil from reaching sensitive wetlands.

"Everyone is in because of weather, whether it's thunderstorms or [high] seas," Wayne Hebert, who helps manage skimming operations for BP, said.

Evacuation

In Louisiana, the coast guard had to evacuate workers and equipment from coastal areas in Terrebonne Parish because of tidal surges that could cause flooding.

in depth

"It's really rough out there," Zac Crawford, a coast guardsman, said.

"We want the oil cleaned up, but we want people to be safe. We don't want to lose anyone working on the spill."

Farther inland, local officials worried the weather could hamper efforts to keep the oil out of Lake Pontchartrain, which so far has not been affected.

"That means they can't get out and start working it. This may be the first test of our outer lines of defence," Suzanne Parsons, spokeswoman for St Tammany Parish, which is on the north side of the lake, said.

Chris Roberts, from Jefferson Parish Council member, said the oil was entering passes at Barataria Bay, home to diverse wildlife.

A day earlier, barges that had been placed in the bay to block the oil were removed because of rough seas.

Progress 'lost'

The storm pushed the oil towards Louisiana's Grand Isle and uninhabited Elmer's Island, dumping tar balls on the beach.

"With this weather we lost all the progress we made," Michael Malone, a marine science technician, said.

The continuing oil spill began in April following an explosion on the BP-operated Deepwater Horizon oil rig, which left 11 workers dead.

Since then, between 1.6m and 3.6m barrels of oil have already poured into the Gulf from the ruptured undersea wellhead, fouling large stretches of US coastline, killing wildlife and devastating coastal fishing communities.

After two previous successes, BP had hoped to install a third system to capture much more oil from the blown-out well by next week but officials said waves as high as four metres would delay it for several days.

Meanwhile the US government on Tuesday accepted offers of help from 12 countries and international organisations in dealing with the spill.

The assistance includes special oil skimming equipment, floating booms designed to contain the oil, as well as personnel.

Overall US officials said 27 countries had offered assistance ranging from vessels and dispersant, to fire boom and technical personnel.