To a backdrop of airstrikes and mounting casualties, American efforts to negotiate a cease-fire in the latest Gaza fighting between Israel and Hamas continued on Wednesday but the struggle to achieve even a brief pause in the fighting emphasized the obstacles to finding any lasting solution.

Israeli airstrikes overnight continued into Wednesday morning, hitting government buildings, the smuggling tunnels under the southern Rafah border crossing and a bridge on the beach road that is one of three linking Gaza City to the central area of the strip. The Hamas health ministry said the Palestinian death toll stood at 140 at noon, with 1,100 injured. At least a third of those killed are believed to have been militants.