A bid to recover a key valve that failed to prevent the blowout of the BP well in the Gulf of Mexico has been delayed because of bad weather, the pointman for the US response to the oil spill said Monday.

"We are in a hold pending calming of the current weather," retired coast guard admiral Thad Allen told reporters, adding that it would be two or three days before the operation could begin.

BP had planned to begin Monday removing the so-called blowout preventer from the busted well and replace it.

It was to be raised to the surface to be examined and held as evidence in an official investigation into the largest maritime oil spill in history.

An estimated 4.9 million barrels of oil gushed into the Gulf of Mexico after an explosion ripped through the Deepwater Horizon rig on April 20, killing 11 workers and sinking the huge offshore platform two days later.

The leak was finally plugged on July 15.