US Secretary of State Colin Powell has expressed concern about the Middle East peace process after Israeli troops killed a Hamas leader in the West Bank.
Israel says it will continue to act against "ticking bombs"
Speaking at a special session of the World Economic Forum in Jordan on Sunday, Mr Powell said the shooting was a "matter of concern" and expressed "regret" that "once again we had an incident that could be an impediment to progress".
The BBC's Paul Wood, in Jordan, says the Americans are furious that the effort to get a ceasefire agreement from Palestinian militants has been set back by Israeli military action.
Israel and the Palestinian Authority disagreed sharply over the significance and details of the killing.
Israeli Prime Minister Ariel Sharon hailed his troops for their "successful and highly important operation" and promised more such attacks if the PA did not tackle militant groups itself.
But Palestinian officials accused Israel of seeking to prevent them securing the ceasefire they have been trying for weeks to negotiate with militants.
Hamas itself vowed revenge but said it would continue to consider a truce.
Mr Powell said the peace process must continue
Mr Powell said after meeting the other roadmap backers - the European Union, Russia and United Nations - that the peace process must keep going forward whatever "incidents" might occur.
German Foreign Minister Joschka Fischer is trying to build regional support for the roadmap, travelling to Lebanon following the World Economic Forum meeting.
"The Middle East will change. It will change rapidly. I think this opportunity should be used," he said in Beirut after meeting his Lebanese counterpart Jean Obeid.
Mr Fischer is set to visit Syria - the effective power in Lebanon - on Monday, where he is expected to urge Damascus to rein in the militant group Hezbollah.
Blamed for bombings
Israel held Hamas commander Abdullah Qawasmeh responsible for three suicide bombings this spring including the Jerusalem attack which killed 17 people on
He was shot dead by an elite Israeli army unit on Saturday night.
The details of Qawasmeh's death are disputed
The Israelis say their forces tried to arrest Qawasmeh and only opened fire after he pulled a gun.
But Palestinian sources said Mr Qawasmeh was shot while standing at the entrance to a mosque.
Hamas leader Abdel-Aziz al-Rantissi - who survived an Israeli attempt to kill him earlier this month - said the killing in Hebron would "not go unpunished".
The attack clearly showed that Israel would "continue to shed Palestinian blood", he said.
In an incident a day after the killing of Qawasmeh, four Palestinians were killed in the town of Beit Hanoun, Palestinian medical sources said.
Palestinian sources said the four had been killed by Israeli tank fire, but the army denied that.
An army statement said they had most likely been killed by the premature explosion of a bomb they were planting, and said there had been no firing in the area at the time.