RAMALLAH, West Bank - Sixty prominent Palestinian officials and intellectuals today urged the public to refrain from retaliation for Israel's assassination of Hamas' founder, saying it would ignite a new round of bloodshed that would only hurt Palestinian aspirations for independence.

The half-page advertisement in the PLO's Al-Ayyam newspaper called on Palestinians to lay down their arms and turn to peaceful means of protest to end Israel's occupation of the West Bank and Gaza Strip.

The ad reflected growing sentiment among many Palestinian leaders and intellectuals that military struggle is not helping the Palestinian cause.

Similar calls in the past have had little impact on public opinion, and today's ad was greeted with little enthusiasm by ordinary Palestinians.

Hamas' founder, Sheik Ahmed Yassin, was killed in an Israeli air strike on Monday, prompting an unprecedented outpouring of outrage on Palestinian streets. Hamas has promised to strike back, saying even Prime Minister Ariel Sharon is a target.

However, the group said it is not targeting the United States, backing off earlier threats against Americans.

On Wednesday, Israeli soldiers stopped a 16-year-old Palestinian youth with a suicide bomb vest strapped to his body at a crowded West Bank checkpoint, setting off a tense encounter with soldiers.

Pictures of the boy, identified as Hussam Abdo, appeared on the front pages of all major Israeli newspapers Thursday, and the incident dominated radio newscasts. Overnight, Israel arrested two of Abdo's classmates, Palestinian sources said.

In new violence, several Israeli tanks moved back into an areas of the Khan Younis refugee camp in the southern Gaza Strip late Wednesday, where some structures were razed earlier in the day.

Military sources, speaking on condition of anonymity, said it was a similar, limited operation. An Israeli helicopter fired a missile at a group of militants, residents said, and a policeman was wounded. Palestinians said 15 buildings were wholly or partly demolished.

The Israeli forces withdrew early today, a military spokeswoman said.

The intellectuals who signed Thursday's ad - including lawmaker Hanan Ashrawi and Abbas Zaki, a leading member of Yasser Arafat's Fatah movement - said revenge attacks would lead to strong Israeli retaliation and further hurt the Palestinian cause.

An Israeli delegation - including Sharon's bureau chief Dov Weisglass and National Security Adviser Giora Eiland - is in Washington this week to discuss the separation plan. On Wednesday, the Israeli team presented one scenario, showing the Americans a map in which six West Bank settlements would be removed in addition to most Gaza communities, an official said.

Speaking on condition of anonymity, he emphasized that no decision has been made yet on which option to implement.