A White House spokesman held Israel responsible on Thursday for the shelling of a UN facility in Gaza this week, condemning the incident as "totally unacceptable and totally indefensible," and calling on Israel to do more to avoid civilian casualties.Israel talks frequently about the importance it places on sparing civilian lives but the United States believes its government and military are not doing enough to that end, spokesman Josh Earnest said at a news briefing. "The shelling of a UN facility that is housing innocent civilians who are fleeing violence is totally unacceptable and totally indefensible," Earnest said.Gaza health officials say more than 1,400 Palestinians have been killed in the battered enclave. Israel says 56 of its soldiers and three civilians have been killed by rockets fired by the Hamas terror group."We believe the Israeli government and the Israeli military need to do more to live up to the own standards that they have set for protecting innocent civilians," Earnest said.Earnest repeated US calls for an immediate cease fire and urged Hamas to stop firing rockets at innocent Israeli civilians.The Pentagon also called on Israel on Thursday to do more to protect civilian life during its military operations in Gaza, saying the conflict was taking too high a toll on civilians.On Wednesday, the IDF, in an initial response to the killing of at least 19 Palestinians in a United Nations-run school in Gaza, said terrorists near the facility had fired mortar bombs and Israeli forces had shot back."Earlier this morning, militants fired mortar shells at (Israeli) soldiers from the vicinity of the UNRWA school in Jabaliya (refugee camp). In response, soldiers fired towards the origins of fire, and we're still reviewing the incident," an IDF spokeswoman said.Jpost.com Staff contributed to this report.