Israeli war cabinet minister Benny Gantz’s centrist party proposed on Thursday a bill to dissolve parliament, showing the growing strains in Benjamin Netanyahu’s government even if the prime minister has enough lawmakers to keep him in office.

The move follows an ultimatum Gantz issued in May, demanding that Netanyahu agree to a day-after plan for the Gaza war by June 8. He threatened to quit the coalition if no such agreement was forthcoming, although the prime minister’s Likud party and…