This much is clear: A devastating blast Monday in Gaza killed five members of the same family – a mother and four children. But whose ammunition was responsible has turned into another bitter dispute as Israeli and Palestinian officials each blame the other.

Palestinians say Israel dropped either a tank shell or a missile into the Gaza house while the family was eating breakfast. The Israeli army says the family members were killed after it fired on militants carrying munitions nearby, sparking a secondary explosion that destroyed the family's home. It says the blast was caused either by "an explosive charge" or from "explosives that members of the terror cell were carrying near the house in which there were uninvolved civilians."

Either way, the ensuing vitriol and the upsurge in violence underscores the need for a Hamas-Israeli cease-fire, yet complicates ongoing diplomatic in Egypt efforts to reach one soon.

Following what Hamas officials called a "massacre" on Monday, the group launched 11 Qassam rockets and nine mortars into Israel's Negev region Tuesday, leading to a few direct hits on homes and buildings, but no serious injuries.

Amid controversy over the deaths of Gazan mother Miyasra Abu Muatak and her four children, Israeli Prime Minister Ehud Olmert Tuesday expressed "deep remorse" for the loss of innocent life, but fundamentally blamed Hamas. He said the Palestinian group's militants were operating in civilian areas and turning residents "into an inseparable part of the war."

Just before a cabinet meeting, Mr. Olmert made reference to ongoing Egyptian efforts to help broker a truce between Israel and Hamas.

"I hope the terror organizations' brutal fighting will cease," he said. "But as long as the terror organizations fire at the [Israeli] South's residents, the IDF [Israel Defense Forces] will continue to operate against them."

Israel's defense minister, Ehud Barak, sounded even less optimistic about a truce with Hamas as he toured Israel's controversial wall – alternatively referred to in Israel as a security barrier or a separation fence.

"Israel is in a state of conflict with Hamas, and not in a state of a cease-fire," Mr. Barak told reporters. "We are not happy when civilians are hurt, but we view Hamas as the one to blame," he added.

Some 30 representatives of various Palestinian factions gathered in Cairo Tuesday to meet with the Egyptian director of intelligence, Gen. Omar Suleiman, to present their positions on a proposed six-month Israel-Hamas truce.

Meanwhile, many Israeli officials are showing reluctance to accept a half-year deal, saying that it would only give Hamas and other Palestinian militant factions a period of time to rearm. On Tuesday, Egypt security officials said it has discovered five tunnels used to smuggle fuel and goods to Gaza. Israel charges that the tunnels are used to smuggle in weapons, as well.

As the rounds of finger-pointing continued, another member of Olmert's cabinet, Interior Minister Meir Sheetrit, expressed doubt in the wisdom of agreeing to such a short cease-fire.

"Aren't children being hurt here?" Mr. Sheetrit asked. "We are at war and have no other way but to fight Hamas. I object to a cease-fire with Hamas which will allow them to continue smuggling weapons."

Part of the difficulty in reaching a cease-fire lies in the deep rifts that now exist in the Palestinian political arena, dividing the Hamas-controlled Gaza from the Fatah-run Palestinian Authority (PA) in the West Bank. One of the demands that Hamas is making as a condition of a cease-fire, says an official trying to mediate between the two warring Palestinian movements, is that Israel agree to open all the crossings into Gaza, especially the Rafah Crossing with Egypt. But the official, who asked not to be named, acknowledged that Israel is not likely to agree to such a scenario without the involvement of the PA and the security forces loyal to PA President Mahmoud Abbas.

Another way in which the Fatah-Hamas split encumbers a deal with Israel for any kind of a truce is the question of whether a cease-fire would apply to the West Bank. Hamas has said in the past year that some of its Qassam rocket attacks on Israel were in retaliation for IDF incursions and arrests of Palestinians in the West Bank. This would indicate that Hamas views any kind of IDF action, be it in Gaza or the West Bank, as a provocation and a legitimate reason for retaliation.

The Israeli military, on the other hand, has shown an unwillingness to agree to stop its operations in the West Bank, believing that to do so would allow Hamas, Islamic Jihad, and even PLO-affiliated militant groups to flourish.

Despite the violence, each side seems primarily concerned with not forfeiting or even hampering what they see as their legitimate military option, be it "resistance" in Palestinian parlance or "deterrence" in Israel's.

"I don't think we can talk seriously about a truce or opening the crossings without a Palestinian national reconciliation deal, and I don't see that happening right way, " says Ziad Abu Amar, a Palestinian political analyst and former cabinet minister in Gaza.

"In the absence of a more comprehensive agreement of national reconciliation, the risk of having such a deal collapse remains higher. In order for it to succeed, it needs to be built on national reconciliation," says Dr. Abu Amar. "But it's too complicated to include all these issues, ending the siege and agreeing to the truce, without involving the PA in Ramallah and Abbas. And if this is the case, we're back to Square One."

All of which is pointing in the direction of a less-than-ideal month of May, when President Bush and other world leaders are due in Israel to celebrate the 60th anniversary of the country's independence.

Mr. Bush is due to visit Israel in mid-May and his administration has been pushing to have a cease-fire in place in advance of his visit. Secretary of State Condoleezza Rice arrives here later this week in attempt to pave the way for the visit and revive Israeli-Palestinian peacemaking efforts.