BP's chief executive is poised to resign before Tuesday's announcement of the energy giant's half-year results, local media reported on Sunday.

The Sunday Telegraph newspaper said that BP CEO Tony Hayward was set to step down before Tuesday, after having been criticised for his handling of the Gulf of Mexico oil spill crisis.

Media reports have been suggesting for days that Hayward would quit his job some time in the coming weeks.

The Sunday Telegraph also said there could be a wrangling over Hayward's severance package under which the CEO is likely to be paid a minimum figure of over one million pounds.

In another development, a vessel charged with drilling a relief well to finally stop the Gulf of Mexico oil spill returned to the gulf well site Saturday after briefly evacuating the area due to a tropical storm.

The drill rig, Development Driller III, was among some 10 ships that evacuated the area ahead of Tropical Storm Bonnie. It was to begin re-attaching to the well site immediately.

U.S. Coast Guard Commander Thad Allen said a first chance to seal the well for good could come in the next three to five days, as response crews quickly scaled operations back up.

The International Energy Agency estimated that between 2.3 million and 4.5 million barrels of crude oil had gushed into the sea as a result of the April 20 explosion aboard the BP-leased Deepwater Horizon oil platform which killed 11 workers and sank the rig.