Intraoperative management of difficult cholecystectomy

A 45-year-old woman undergoes elective open cholecystectomy for symptomatic cholelithiasis. Intraoperatively, the cystic artery is identified and ligated. However, the surgeon notes that the common bile duct (CBD) is densely adherent to the gallbladder fundus and cannot be safely dissected. Which of the following is the most appropriate next step?