As BP opens its checkbook to pay damages related to the Gulf of Mexico oil spill, it is beginning to do battle over a high-stakes question: Who else bears liability?

Some of the companies involved in the drilling operation are laying the groundwork to argue: not us.

In recent regulatory filings and other statements, they deflect responsibility, setting the stage for what is likely to be a years-long legal battle over corporate liability for a disaster whose financial toll is already estimated in the billions.

Halliburton, a project contractor, says it followed instructions from the well owner, a group led by BP. Transocean, which leased the rig to BP, says it was liable only for surface spills — not those emanating from the sea bottom. Anadarko Petroleum, a venture partner, implies that it may be off the hook because BP likely engaged in ‘gross negligence or willful misconduct.’ Schlumberger, another contractor, says it is figuring out if it is contractually insulated from liability.

‘The responsibility for this event will be debated for some time, and there is a lot of confusion around where liabilities begin and end,’ said Bart Nash, a spokesman for the London-based Lloyd’s marketplace, whose insurance syndicates face hundreds of millions […]