The possible showdown comes after Hamas' chief bomb-maker, Mohiyedine Sharif, was found murdered in the West Bank.

Hamas blamed Israel for the killing and vowed to avenge Sharif's death, raising fears of possible suicide bombing attacks during the Passover holiday.

But the Palestinian Authority this week cleared Israel of blame, saying that Sharif had been murdered by other Hamas members in an apparent internal struggle in the militant Islamic group.

A Palestinian official said Monday that five Hamas members had been detained in connection with Sharif's death. A sixth man, who was believed to have shot Sharif, was still at large.

Israel, which had adamantly denied any involvement in the murder, welcomed the Palestinian Authority's announcement.

But Hamas, which threatened new terrorist attacks, called the latest statements by the self-rule authority "lies," resulting from American and Israeli pressure.

The self-rule authority announcement was the latest twist in the inquiry into the circumstances of Sharif's death.

The militant's body was identified by Palestinian police on April 1, several days after it had been found next to a bombed vehicle near the Palestinian-controlled town of Ramallah in the West Bank.

Palestinian security officials had initially reported that the car explosion was apparently a "work accident" involving Hamas terrorists planning to carry out an attack inside Israel. At first, Palestinian officials could not identify the body of the dead man.

But Palestinian security officials informed their Israeli counterparts that they believed the body was Sharif, and Israeli security forces asked that DNA testing be conducted.

The murder came amid recent warnings from Israeli intelligence officials that Hamas members were planning to carry out a massive attack in Israel.

Those concerns were heightened after Palestinian officials confirmed that the body was Sharif.

The head of Israel's General Security Service, Ami Ayalon, met with Palestinian Authority Chairman Yasser Arafat last week to discuss the Hamas threat and the effect a terror attack could have on the faltering peace process.

Ayalon reportedly told the Israeli Cabinet Sunday that Arafat had agreed that an act of terrorism could undermine the effort to bring about a further Israeli redeployment in the West Bank.

Sharif, 32, was seen as the heir to Yehiya Ayash, who was killed by a booby-trapped cellular phone in the Gaza Strip in January 1996. Ayash had topped Israel's most-wanted list for masterminding a series of suicide bombings that killed scores of Israelis.

Sharif, too, was on Israel's list of wanted Hamas terrorists for his involvement in planning several suicide bombings.

Ayash's death set off a wave of suicide bombings in early 1996, and Hamas officials issued a leaflet Wednesday calling on Arabs and Muslims worldwide to attack Jewish targets in revenge.

But Hamas officials also offered another theory that blamed Sharif's death on the Palestinian Authority.

Hamas spokesman Abdel Aziz Rantissi was quoted as blaming the Palestinian preventive security service for murdering Sharif. He later denied his remarks.

Palestinian Authority official Nabil Sha'ath, who last week had blamed Israel for the killing, said Monday that the self-rule authority had conclusively determined that Sharif was killed as part of an internal feud in Hamas.

"I can now say that Israel was not responsible," Sha'ath was quoted as saying.

Prime Minister Benjamin Netanyahu said he regretted that "senior officials in the Palestinian Authority hastened to point a finger at Israel."