As Israeli forces killed more than 100 Palestinians on Sunday, Israeli Prime Benjamin Netanyahu vowed to continue the assault on Gaza for "as long as is required," citing the backing of foreign allies that has "laid the diplomatic foundation that has given us international credit to operate." The Obama administration has provided critical support, claiming Israel has acted in self-defense and blaming Hamas for the civilian toll. But on the conflict's bloodiest day, the White House began showing mild signs of apprehension. President Obama spoke to Netanyahu for the second time in three days and raised "serious concern about the growing number of casualties." Meanwhile, Secretary of State John Kerry made the rounds of Sunday television talk shows to publicly defend Israel's assault on Gaza. But in a private phone call caught on camera in between commercial breaks, Kerry appeared to speak sarcastically about the massive civilian toll in the attacks he was publicly defending. The White House says Kerry will travel to Cairo today to work an end to hostilities based on a return to the November 2012 ceasefire. Max Blumenthal, a best-selling author and senior writer for Alternet, says the Obama administration has practiced "hollow diplomacy," in order to "legitimize Netanayahu's ground operation and create political space for the kind of massacres that we have been witnessing. ... This is an absolute failure of U.S. diplomacy and an abdication of leadership by Barack Obama who says that he is heartbroken by these images that he is witnessing from the Gaza Strip, as he oversees and authorizes the shipment of the very weapons that are used to bombard hospitals."