Lebanon's crisis deepened yesterday with the opposition spurning a plea for dialogue from the pro-Syrian president and as a UN envoy said he feared another high-profile political killing in the country. Opposition figures led by veteran Druze politician Walid Jumblatt rejected an appeal for talks that President Emile Lahoud issued Saturday after a bomb blast in a Christian quarter injured 11 people and sparked fears of a return to sectarian violence here. Lahoud later scrapped plans to attend an Arab summit in Algiers this week.The opposition rejection means that an ominous standoff between anti-Syrian opponents and the current leadership is set to continue in an atmosphere of mounting political tension that followed the assassination Feb. 14 of former prime minister Rafik Hariri. A special United Nations envoy to Lebanon and Syria, meanwhile, warned that under current circumstances Lebanon could suffer another political killing. "I am truly worried about the possibility that a major Lebanese figure could be assassinated," envoy Terje Roed-Larsen said in remarks carried yesterday by Beirut Arabic-language newspapers. "I had sensed trouble before the assassination of Hariri."