The army caused massive devastation in the Jenin refugee camp
But UN Secretary General Kofi Annan has sent the three existing members of the inquiry panel to Geneva for preliminary meetings, before they head to the region on Saturday - one day behind schedule.
Israel complained that no military or counter-terrorism experts had been appointed to the panel, which Israeli officials say was set up to "find Israel guilty" of committing a massacre.
He is due to meet Palestinian leader Yasser Arafat in his besieged Ramallah compound later on Tuesday, three weeks after an EU mission was refused access to Mr Arafat by Israel.
International condemnation of Israel's military actions in the West Bank continues, with Egyptian President Hosni Mubarak accusing Israel of using "state terrorism" to crush "legitimate Palestinian resistance" to Israel's 35-year occupation of Gaza and the West Bank.
Speaking on Egyptian TV, Mr Mubarak - whose country has a long-standing peace treaty with Israel - said the Israeli prime minister's "barbaric and systematic aggression" demonstrated a lack of "any clear vision of peace".
Team members
Palestinians, who accuse the Israeli army of killing hundreds of people in Jenin, are accusing Israel of trying to undermine the integrity of the fact-finding process.
"This is another flagrant violation of relevant Security Council resolutions and of course a violation of international law," said the Palestinian observer at the UN, Nasser al-Kidwa.
Israel insists that those killed were overwhelmingly hardline Palestinian militants who elected to fight to the death after Israeli troops gave them a last chance to surrender.
Mr Annan named former Finnish President Martti Ahtisaari to lead the UN fact-finding mission.
The team also includes Cornelio Sommaruga, former president of the International Committee of the Red Cross, and Sadako Ogata, the former UN High Commissioner for Refugees.
Both the UN relief agency for Palestinian refugees and the ICRC have alleged that the Israeli army violated human rights during the 10-day operation in Jenin by preventing emergency teams from rescuing people trapped under buildings.
Israel's ambassador to the UN, Yehuda Lancry, said the UN team's mandate should cover not only the Israeli operation but also "the terrorist network which has flourished in the Jenin refugee camp".
The team also includes retired US General William Nash and Peter Fitzgerald of Ireland, but only in an advisory capacity for military and police issues, respectively.
A statement from Mr Annan's office said the delay would allow consultation about adding experts to the panel "as deemed necessary".
Reports on Wednesday said Israel refused to grant landing permission to a Greek aid flight to Tel Aviv carrying 12 rescue workers destined for Jenin and Nablus, which was also devastated during Israel's three-week offensive.
Further bloodshed
Tensions have risen sharply in Gaza - spared during the Israeli offensive - with six Palestinians killed in two separate incidents, one involving three 14-year-old schoolchildren shot dead as they tried to enter a Jewish settlement.
Israeli forces also killed two people during a raid on a Palestinian-ruled village near Hebron in the West Bank, as the army continues isolated security sweeps and assassinations.
On Tuesday, masked Palestinians shot dead three suspected informers in Hebron after a local head of the militant al-Aqsa Martyrs brigade was killed in an Israeli missile strike.
Israel launched its offensive to root out what it calls the Palestinian "infrastructure of terror" following a wave of suicide bombings that killed scores of people in Israeli cities.