A 32-year-old multiparous woman at 40 weeks + 5 days gestation is admitted for induction of labor due to post-term pregnancy. Cervical examination reveals a Bishop score of 9 (2 cm dilation, 80% effaced, soft cervix, anterior position, −1 station). Fetal heart rate is reassuring. Oxytocin infusion is initiated at 2 mIU/min and increased by 2 mIU/min every 40 minutes. After 6 hours of augmentation, the patient is in active labor with contractions every 2–3 minutes. However, cervical dilation has plateaued at 6 cm for the past 2 hours, and the fetal head remains at −1 station. What is the most appropriate next step in management?