Netanyahu has been seeking to head off political pressure over Gaza ahead of April 9 elections, in which he faces a strong challenge from former military chief Benny Gantz.
"In recent days I gave instructions to fortify forces, to add vehicles, to be prepared for a comprehensive campaign," he said during the inauguration of a new road in northern Israel.
The premier, who was speaking after visiting military forces on the Gaza border, noted however that a war would be the last option.
"All Israelis should know that if a comprehensive campaign is required, we will enter it strong and safe, after we have exhausted all other possibilities," said Netanyahu, who also serves as defense minister.
Palestinian militants had on Monday fired a long-distance rocket from the Gaza Strip, hitting a house north of Tel Aviv and wounding seven Israelis, triggering Israeli air strikes and further Palestinian fire at southern Israel.
Netanyahu beefed up the military presence near Gaza, but by Wednesday the fighting had abated after Hamas announced a ceasefire brokered by Egypt.