A primipara is in labour for 19 hours, amniotic fluid has discharged 7 hours ago. Pelvic sizes are: 24-25-29-18 cm. Fetal position is longitudinal, head presents and is engaged to pelvic inlet. Fetus heart rate is 160 bpm. No autonomous urination. Vaginal inspection: cervix is smoothed and 8 cm dilated. Head is presented, sagittal suture occupies the transverse diameter of pelvic inlet; small fontanel is on the left. Lower uterine segment is tender on pressing. What medical tactics should be chosen?