At the same time it was reported that the US Middle East trouble-shooter, Dennis Ross, was returning to the region later this week with a revised formula for kick-starting Israeli-Palestinian peace negotiations.
The draft's key elements will remain an Israeli settlement freeze, balanced by a Palestinian drive against violent Islamic resistance to the Oslo accords.
But in the wake of the twin suicide explosion in a Jerusalem market, which killed 13 Israeli civilians last Wednesday, Mr Ross is expected to strengthen demands that Yasser Arafat curb the men of violence.
Israeli security sources admitted yesterday that they still had no firm lead on the identity of the two bombers in the Mahane Yehuda market. Forensic tests have eliminated two young Palestinians who went missing over a year ago from a village near Hebron.
Investigators are checking the possibility that the bombers came from abroad. As if to conceal their origins, the pair removed all labels from their clothing.
The Israelis are inclined, however, to take claims of responsibility by Hamas, the Islamic Resistance Movement, at face value. Hamas, the larger and more political of the two Palestinian Islamic movements, perpetrated 10 of the 14 previous mass attacks inside Israel since the 1993 peace agreement. Its bombers killed 94 of the 139 victims.
Hamas has a wider agenda than its rival, Islamic Jihad. It aspires to influence the future of Palestine, as a party not just a ginger group. It runs nursery schools, clinics and youth clubs. It builds mosques. It educates and mobilises in the cause of "flying the flag of Allah over every part of Palestine". Recognition of Israel is sacrilege.
Hamas operates through separate political and military wings. The visible leadership invariably denies knowledge of armed activity. Yet Hamas has always embraced violence as a legitimate instrument.
It traces its roots to the battle against Zionist colonisation in the 1930s. Its military wing takes its name from Izeddin el-Kassem, a legendary fighter of those days.
A Hamas leaflet distributed in October 1990 called for Jews to be murdered and their property burned. "Every Jew," it said, "is a settler and it is our duty to kill him."
Ideologically, the movement was inspired by the Egyptian Muslim Brotherhood. Cells begun operating in the West Bank and Gaza Strip after the Israeli conquest in 1967, but a formal organisation was founded only in 1978 by Sheikh Ahmed Yassin. The sheikh has been in an Israeli prison since 1989, convicted of organising terrorist cells and operations.
Recent opinion polls suggest that, despite the disenchantment with the Oslo peace, Hamas enjoys limited support in the Palestinian street.
Khalil Shikaki, a Nablus-based political scientist, has, however, monitored a doubling in support for violence (from 20 per cent to 40 per cent) since Benjamin Netanyahu began building Jewish homes in East Jerusalem in March. Yet the Palestinians are still fighting shy of the Islamic groups.
"Hamas has been losing steadily," Dr Shikaki said, "not because Hamas's message or Hamas's means are rejected.
"It is more because Hamas is divided between those who insist on ideological purity and the pragmatists who would like to see changes in the ideology to reflect the reality on the ground."