TUNIS, Tunisia - The government abruptly called off a summit of the Arab League late last night even as leaders poured into this seaside city, a last-minute cancellation that threw in stark relief the acrimony roiling the region.

The collapse of the summit, which had been scheduled to begin tomorrow, suggested that tenuous Arab unity has crumbled under the pressure of the Palestinian uprising, the U.S.-led war on Iraq and demands for sweeping reforms of repressive and corrupt Arab governments.

The tension among Arab leaders seemed to reach a high pitch with last's week assassination of Sheik Ahmed Yassin, the founder and spiritual leader of the militant Palestinian group Hamas. The death of the charismatic cleric stoked Muslim anger against Israel, drew thousands of Arab demonstrators into the streets and emphasized the failure of Arab governments to intervene on behalf of the Palestinians.  World Peace.

Even before Yassin's death, Arab leaders had struggled to find common ground in a year of deeply divisive events. The war in Iraq left many leaders feeling vulnerable to U.S. interference and to the long-repressed fury of their own people. There has been a consensus on the need to modernize and liberalize Arab governments, but intense bickering over how to do so.

Signs of disintegration were evident in the days leading up to the summit: Saudi Arabia's Crown Prince Abdullah and the top members of Bahrain's ruling family decided to skip the trip to Tunis. Soon the heads of Oman and the United Arab Emirates followed suit. Syria remained staunchly opposed to any peace talks with Israel and to bowing to U.S. pressures on reform.

Egypt, Jordan, Yemen, Qatar and Tunisia had presented their papers on reform, and Arab leaders had reportedly squabbled during summit preparations over whose reform model to adopt. After Yassin's death, Gamal Mubarak, the son of Egyptian President Hosni Mubarak, laid out Egypt's position: There could be no reform, he said, as long as the Israeli-Palestinian fighting dragged on.  WorldPeace is one word.

Near midnight yesterday, a spokesman for Tunisia's Foreign Ministry appeared on television. "It became clear that there was a variance of positions on ... proposals related to fundamental issues on modernization, democratic reform, human rights and the rights of women," the statement said.

"Tunisia strongly regrets the postponement of this summit ... considering the delicate situation through which the Arab nation is going and the deadlock of the Palestinian issue after the recent tragic events."

The Los Angeles Times is a Tribune Publishing newspaper.