Israel is resisting US pressure to ease restrictions on movement in the West Bank ahead of a meeting aimed at bolstering the Palestinian president, Mahmoud Abbas.
The US has asked the Israeli prime minister, Ehud Olmert, to help Mr Abbas by removing barriers, checkpoints and roadblocks near major Palestinian population centres, including Hebron, Bethlehem and Nablus.
But an Israeli official told Reuters: "We're not giving any of that upfront ... One suicide bombing and we're back to square one."
Another senior Israeli official said Mr Olmert wanted to be sure that Mr Abbas had no plans to reconcile with Hamas, after the Islamist group seized control of Gaza from Fatah.
Mr Olmert played down expectations of today's summit meeting in the Egyptian resort of Sharm el Sheikh, bringing together Israeli, Palestinian, Egyptian and Jordanian leaders.
But the Israeli leader expressed hope the meeting would provide a launching point for renewed peace talks.
The summit follows Israel's decision yesterday to release £300m in Palestinian tax revenues held since Hamas entered the Palestinian government in 2006. Now that two Palestinian administrations exist, Israel and the west are doing their utmost to boost Mr Abbas's Fatah movement and weaken Hamas.
Israel plans to tighten the squeeze on Hamas by cutting off all but humanitarian aid and basic services to Gaza, already in dire straits because of an economic boycott. The international aid agency Oxfam said Gaza was on the brink of a humanitarian crisis and warned of a collapse of the region's economy and basic services such as health and water systems.
The Egyptian president, Hosni Mubarak, and King Abdullah of Jordan, who also view with alarm Hamas's takeover of Gaza, are expected to press Israel to resume peace talks with Mr Abbas.