In a 37-year-old primigravida the labor lasts for 10 hours already. Contractions last 20–25 seconds and occur every 6– 7 minutes. The fetus is in a longitudinal lie with cephalic presentation, the head is pressed against the entrance to the lesser pelvis. Vaginal examination has shown that the uterine cervix is up to 1 cm long and allows 2 finger-widths. The amniotic sac is absent. Make the right diagnosis: