Even as the international community's calls for "de-escalation" are becoming more urgent, the fighting in Gaza is only intensifying. Following Wednesday's killing of the head of Hamas's military wing, the air strikes on Gaza and the rocket attacks into Israel have been steadily increasing, and the death toll with them.

For all the human tragedy, the periodic conflicts in Gaza provoke a sense of weary inevitability. What is different this time is that the latest spasm takes place in a region reshaped by the Arab Spring. Under Hosni Mubarak, Egypt was an ally of the US committed to peace with Israel; now its government is led by a member of the same Muslim Brotherhood that counts Hamas among its affiliates. Of the many tests that Egypt's first democratic President has faced since his election in June, the conflict in Gaza is perhaps the most hazardous. Mohamed Morsi is under pressure at home to stand up for beleaguered Palestinians, reversing Mubarak-era policies widely considered unduly supine. But regional instability will hit Egypt hard, and its ailing economy needs Western aid.

So far, Mr Morsi has played his cards carefully. He has condemned "Israeli aggression", withdrawn Egypt's ambassador to Tel Aviv and sent Prime Minister Hesham Kandil to Gaza. But he has not offered Hamas military support, or threatened action against Israel.

The danger is that he will be bounced by events. After three days, there are few signs of progress. Egypt wants the US to restrain Israel; the US is calling on Egypt to put pressure on Hamas. Neither side wants to blink first. Even the three-hour ceasefire for Mr Kandil's visit did not hold, and reports of tanks on Gaza's border add weight to Israeli talk of a land invasion.

Mr Morsi's balancing act turns the spotlight on to the relationship between Israel and Egypt and leaves the peace brokered by Anwar Sadat and Menachem Begin under threat for the first time in more than 30 years. In increasing the pressure on Cairo, the latest Israeli action in Gaza is far more dangerous than its predecessors. Without rapid "de-escalation", the prospects are alarming: for Israel, for Gaza and for the wider region.