JERUSALEM?A spike in Mideast violence Sunday dampened prospects for a U.S. mediation effort, as a Palestinian teenager died in a clash with Israeli soldiers and Israeli helicopters blasted buildings in Gaza after a mortar shell killed an Israeli soldier.

The violence came a day before Assistant Secretary of State William Burns and new envoy Anthony Zinni, a retired Marine Corps general, were to begin their peace mission there.

The Americans hope to quash Israeli-Palestinian fighting before it undermines the U.S.-led coalition against international terrorism.

The mediators arriving Monday were to meet with Israeli Prime Minister Ariel Sharon and Foreign Minister Shimon Peres.

Palestinian leader Yasser Arafat was on a trip to Arab countries and was not expected back until Wednesday. In Cairo on Sunday, he charged Israel with “continuous aggression.”