The Palestinian leadership is facing tough US and international pressure to crack down on militant groups following a roadside bombing that killed three US security men in the Gaza Strip.
Washington was sending a FBI team to search for the perpetrators and made clear that the United States, which has watched continued bloodshed shatter its peace plan, would play a leading role in the investigation.
The United States blamed the Palestinian Authority for security lapses that led to the killing of the Americans and took a tough line on the terms for resuming Middle East diplomacy.
President George W. Bush said the Palestinian authorities should have acted long ago "to fight terror in all its forms."
"The failure to create effective Palestinian security forces dedicated to fighting terror continues to cost lives," he said in a statement on the bombing.
Palestinian Prime Minister Ahmed Qurie pledged cooperation and Palestinian President Yasser Arafat told BBC television he was mobilising his security team to find the attackers.
A roadside bomb, apparently detonated by remote control, reduced a armour-plated jeep in a US convoy to mangled wreckage and gouged a deep crater in the road.
Palestinian militant groups denied involvement in the attack, but the United States, the United Nations, and Europe blamed the bombing on lax Palestinian security.