Hague said Hamas, Gaza's militant rulers, "bears principal responsibility" for initiating the violence and must stop all rocket attacks on Israel. But Hague also made clear the diplomatic risks of an Israeli escalation.

"A ground invasion is much more difficult for the international community to sympathize with or support, including the United Kingdom," he said.

Israeli officials say the airstrikes are aimed at ending months of rocket fire out of the Hamas-ruled territory. Israel began the offensive with an unexpected airstrike that killed Hamas' military chief, and since then has targeted suspected rocket launchers and storage sites.