Arab leaders remain as deeply divided as ever over the Palestinian question
Arab divisions over the Gaza crisis have re-emerged at a summit in Kuwait.
Egyptian President Hosni Mubarak said Hamas had invited the Israeli attacks on the Gaza Strip by refusing to extend a truce that expired in December.
Syrian President Bashar al-Assad said Arab leaders should adopt a resolution declaring Israel a terrorist entity, and support Palestinian resistance.
Reports say the Saudi king hosted a lunch for five other leaders on the summit sidelines to try to heal rifts.
They included the Qatari and Syrian leaders, among the sternest Arab critics of Israel's military campaign, and Egypt and Jordan, who have long-standing alliances with Israel.
Qatar's Prime Minister Sheikh Hamad bin Jasim al-Thani said the Saudi lunch achieved its goals towards reconciliation, but gave no further details.
Earlier, the Saudi king, Abdullah bin Abdul Aziz, said his country would donate $1bn to finance reconstruction in the heavily-bombed Gaza Strip.
The sum is about half of what Arab officials have said they hope to raise.
"I call on you in the name of God... that we rise above our difference and defeat the expectations of our enemies and we take an honourable stand," King Abdullah said at the opening session.
Palestinian Authority President Mahmoud Abbas - whose Fatah faction was ousted by Hamas from control of Gaza in 2007 - called for immediate reconciliation talks.
"What is required today... is to form a national unity government which will then conduct presidential and legislative elections simultaneously," he said.
Mr Assad said: "We should show our clear support for the Palestinian resistance. I suggest this summit officially call the Zionist entity a terrorist entity."
Mr Mubarak warned that regional powers were trying to exploit Arab differences and reiterated that a peaceful settlement remained the only option.
"It should be taken seriously by Israel and international big powers... Middle East peace is an urgent necessity," he said.
The two-day summit had been billed as a chance for Arab leaders to sidestep political divisions and focus on economic matters.
Subjects for discussion included a pan-Arab common market and customs union, and ambitious joint infrastructure projects.
Correspondents say several pro-Western Arab leaders have faced strong criticism from their citizens, outraged both by Israel's attacks on Gaza and their governments' inability to end the violence.
Egypt and Saudi Arabia shunned a summit hosted by Qatar last week which called for freezing ties with Israel. Syria pronounced the 2002 Arab peace initiative as dead.
Cairo has face particularly angry criticism that it co-operates with Israel's blockade of Gaza.
Sheikh Hamad told the Qatari-owned al-Jazeera channel that there had been misunderstandings in Doha and expressed the hope "we can put our hands together... to strengthen the Arab position".
Arab League Secretary General Amr Moussa told Arab leaders it was time for the body he chairs to demonstrate it had a role.
"The Arab ship is really sinking and Kuwait's summit... might save it," Mr Moussa said.
Israel launched its attack on Gaza on 27 December after a six-month ceasefire with the Hamas movement lapsed.
More than 1,250 Palestinians, about half of them civilians, were killed, as well as 10 Israeli soldiers and three civilians.
Israel and Hamas have each declared a ceasefire, but it remains very shaky, analysts say.