It would most likely take the military days or weeks to call up the reserve forces necessary for a push into Gaza City and to allow time for the forced evacuation of tens of thousands of Palestinians from the new areas of combat. If the government decides to go further, the military believes it could seize the remaining parts of Gaza within months. Who would govern? Mr. Netanyahu said on Thursday that Israel did not want permanent authority over Gaza. “We don’t want to keep it,” he said. “We don’t want to govern it. We don’t want to be there as a governing body. We want to hand it over to Arab forces.” Arab states could agree to participate in an international force, possibly handling security and administration, perhaps with foreign peacekeepers or contractors. But they would most likely want approval from, and a role for, the Palestinian Authority, which currently administers part of the West Bank and governed in parts of Gaza before Hamas came to power in 2007.