Plans are underway to conduct a comprehensive strategic review of the company and sell all its refineries in Philadelphia and Marcus Hook.
Sunoco said it will now focus on its more profitable logistics and retail businesses.
If a suitable transaction to divest the refining business cannot be met, the company plans to shut down its main processing units at the facilities in July 2012.
In addition, the company expects to record a pretax non-cash charge of between $1.9bn and $2.2bn in the third quarter of 2011 related to impairment of the plant and equipment in the refineries.
Additional pretax charges of up to $500m, primarily related to contract terminations, staffing costs and severance, may be incurred in the event.
Credit Suisse Securities has been retained to assist in the review process.
