The Bush administration has repeated its opposition to so-called "targeted killings" by Israel following the rocket attack Monday that killed a senior Palestinian figure in the West Bank.
Officials here are monitoring the clashes with growing concern and with State Department spokesman Richard Boucher saying the escalation of recent days threatens to "overwhelm" any chance of restoring calm and getting the parties to implement the peace blueprint of the Mitchell committee.
Briefing reporters, Mr. Boucher said both sides know exactly what needs to be done to end the confrontation - and that "above all" the Palestinian Authority needs to take "sustained and credible" steps to pre-empt anti-Israel terrorism and arrest those responsible.
He said Israel for its part must take the economic and security steps necessary to alleviate what he termed "pressure, hardships, and humiliations" of the Palestinian people.
The spokesman said Israel has a right to defend itself in the face of terrorism but that both sides must avoid actions that make the situation worse - including attacks like the Israeli rocket strike on a Ramallah apartment block early Monday that killed Mustafa al-Zibri, head of the radical PFLP Palestinian faction.
"We think Israel needs to understand that targeted killings of Palestinians don't end the violence but are only inflaming an already volatile situation, making it much harder to restore calm," said Mr. Boucher. "We're deeply troubled by the fact that civilians, including more than 20 American citizens - some of whom were children - were living in the building which was attacked over the weekend."
Mr. Boucher had no reaction to a call from a PFLP spokesman in Damascus for attacks on American interests in the Middle East after the killing of Mr. al-Zibri.
However, he said the United States has given Israel no "green light" for attacks on prominent Palestinians, and said Israel's use of U.S.-supplied military hardware in such operations is an "issue of concern" for the Bush administration.