The US contractor that worked for BP on the Deepwater Horizon oil rig has admitted destroying evidence relating to its explosion in 2010 - an accident which sparked the biggest oil spill in US history.
Halliburton said on Thursday it would plead guilty to suppressing crucial information which BP wanted to use in its legal battles over the disaster off the Louisiana coast.
The Deepwater Horizon explosion killed 11 men and caused billions of dollars worth of damage to fishing and tourism businesses in the region. So far, it has also cost BP more than $US40 billion ($43 billion) in legal costs and compensation payouts, which are still mounting, as up to 10,000 new claims are filed each month.
Halliburton, based in Houston, Texas, admitted destroying computer simulations, in a twist of events which will raise new questions over America's treatment of BP.
The simulations showed that there was no difference between certain technical specifications which Halliburton recommended to BP, and the structure which the British oil giant ultimately opted for.
Halliburton had advised BP to include 21 "centralisers" in the oil well being drilled by Deepwater Horizon. However, BP chose to use six of the metal protrusions, which are fixed to the outside of a long metal pipe lowered into the well, and used to keep it centred so it does not crash into the walls of the well.
BP had asked Halliburton for the simulation numerous times, and in 2011 resorted to legal action.
It claimed in a lawsuit that Halliburton had "intentionally" destroyed evidence in order to "eliminate any risk" that it would be used against Halliburton at trial.
Halliburton's guilty plea must be approved by the courts before it is formally accepted, or before the Department of Justice can impose the maximum fine of $US200,000.