Speaking Sunday on "Meet the Press," Livni says the Israeli assault came because Gaza's Hamas rulers were smuggling weapons and building up "a small army."
But, she said, "Our goal is not to reoccupy" the Gaza Strip.
Some 280 Palestinians have died in the first 24 hours of the campaign against Gaza rocket squads - most of them Hamas police.
Livni's comments come as Israel's Cabinet authorized a, suggesting plans to expand the offensive with ground forces against Gaza rocket squads.
Israel launched some 250 airstrikes over the first 24 hours of the campaign. Infantry and armored units were already headed to the Gaza border for a possible ground invasion.