Failure to restart Israeli-Palestinian negotiations could stir unrest in the West Bank, the IDF's top commander in the territory warned Tuesday.
Kerry has visited the region four times since taking office in February to try to revive negotiations on the terms of Palestinian statehood that broke off in 2008.
Kerry is trying to bridge wide gaps between the two sides on the starting point for negotiations, and it is not clear if he has made progress. Earlier this month, Kerry called his mission the last chance for resuming negotiations.
"The last couple of months of very intensive American involvement also had some positive influence on the ground," Alon told the Jerusalem Center for Public Affairs, a think tank.
If Kerry's efforts fail, "I'm afraid we will see the escalation ... strengthen," he said in halting English.
Kerry is expected to return to the region soon, but the dates have not been set.
Earlier Tuesday, assailants slashed the tires of 28 cars and sprayed graffiti reading "Arabs out" on walls in Abu Ghosh, an Arab Israeli town near Jerusalem.
Police said they suspected a hate crime. There have been a string of similar incidents linked to Jewish extremists in recent years.
Vandals have targeted mosques, churches, dovish Israeli groups and even Israeli military bases to protest what they perceive as the Israeli government's pro-Palestinian policies.
The acts are widely condemned by Israeli leaders, but arrests have been rare.
President Shimon Peres told Abu Ghosh Mayor Salim Jaber that the vandalism "is racist behavior which crosses a red line" and that he condemns "any expression of racism and vandalism."
Peres' office quoted Jaber as saying the attack would not affect relations between the town and its Jewish neighbors. "We know that this is the act of a small group which seeks to destroy the good relations, but we are stronger than them," Jaber said.
Israeli Prime Minister Benjamin Netanyahu said the vandalism in Abu Ghosh "contradicts Jewish law and the values of our people and our country."
Abu Ghosh, a 20-minute drive from Jerusalem, is a popular with Jewish Israelis because of its restaurants and cultural events.
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