The militant Palestinian groups Hamas and Islamic Jihad said they had suspended suicide attacks against Israel until further notice, helping to ease mounting strains within the Palestinian Authority.
The show of solidarity seemed to be aimed at halting increasingly bloody fighting between Palestinian police and militants, which reached a climax yesterday when six people were killed and over 80 wounded in a gun battle in Gaza.
The clashes, which followed efforts by Palestinian President Yasser Arafat to rein in militants, were the worst since the Palestinian Authority was set up in 1994 and marked one of the most serious internal challenges made to Mr Arafat's leadership.
The United States, which put pressure on Mr Arafat to suppress militant groups after 29 Israelis were killed in recent suicide bombings, expressed wariness at the announcements and demanded he carry on with his crackdown.
"I realize they've said they won't conduct suicide bombings. That has to lead to the conclusion that maybe someday they'll say they will. The point is that the Palestinian Authority needs to make sure that they can't," State Department spokesman Richard Boucher told reporters in Washington.
The decision by Islamic Jihad did not appear clear-cut on Saturday as an Islamic Jihad official in Beirut denied the group was halting attacks and another official in the Gaza Strip said it would not necessarily follow Hamas's lead.
Hamas's military wing posted a statement on its Web site saying it would uphold the decision to suspend suicide attacks against Israel, although it included a proviso.
"If the enemy violates this then we...will be free of our promise and the decision to halt attacks will be canceled. An eye for an eye and a tooth for a tooth," the statement said.
Palestinian cabinet minister Saeb Erekat said the decision by Islamic militants put the ball in Israel's court.
"The Authority sees the steps taken by Hamas and the Islamic Jihad as a positive response and now Israel has to immediately withdraw its troops from reoccupied Palestinian areas, and has to stop assassinations and lift the siege," Mr Erekat said.