A federal judge has outlined a new structure for a trial of Gulf oil spill claims that wouldn't be resolved by a proposed class-action settlement between BP PLC and a team of plaintiffs' attorneys.

In an order Wednesday, U.S. District Judge Carl Barbier said the trial scheduled to start Jan. 14, 2013, will be conducted in at least two phases.

The first phase will explore possible causes of the April 2010 well blowout that triggered a deadly rig explosion and led to the massive oil spill. The second phase will address efforts to stop the flow of oil from BP's Macondo well.

Barbier said he may issue partial rulings at the end of each phase.

A trial originally scheduled to start in February was postponed indefinitely after the settlement was announced.