Rival Palestinian leaders began crisis talks on Wednesday in the Muslim holy city of Mecca in the hopes they could end their deadly factional fighting.
The summit in Saudi Arabia is also seen as the last chance to resolve differences between the feuding Palestinian factions that have threatened to ignore civil war.
"We came here to agree and we have no other option but to agree," the exiled leader of the hardline Hamas group, Khaled Mashaal, told the inaugural ceremony.
Saudi King Abdullah organized the talks between Mashaal and Palestinian President Mahmoud Abbas of the moderate Fatah party.
Abbas said he and his Fatah delegation had told all their supporters that "we will not leave this holy place until we have agreed on everything good, with God's blessing."
Abbas met Hamas leaders around a table in a palace overlooking the Haram mosque, which houses Islam's revered shrine, the Kaaba.
In reference to the violent gun battles that left more than 30 people dead in the past week, Mashaal told Abbas they had to tell their supporters to honour the tenuous truce that took hold on Sunday.
"We want to give a message to the nation, and the world, to create a positive atmosphere for these talks," Mashaal said.
Earlier Wednesday, Palestinian Prime Minister Ismail Haniyeh, Mashaal, and other members of the Hamas delegation called on Abbas in Jiddah.
Hamas delegate Abdel Rahman Zaidan described the meeting as "positive" and said it was clear Abbas shares with Hamas the desire to reach an agreement.
Hamas and Fatah have held numerous discussions on a national unity government but talks have foundered on the composition of the regime and its position on agreements signed with Israel.
Hamas has long refused to recognize the peace accords Israel signed with the Palestine Liberation Organization, of which Fatah is the major member.
An agreement between the rival factions is also vital if the peace process is to resume.
Fatah and Hamas have been locked in a power struggle that has killed more than 90 people since December.
Israel has refused to hold discussions since Hamas won legislative elections in January 2006.
Abbas, a moderate who was elected separately, is hoping for an agreement on a coalition government in which Hamas will give some degree of recognition to previous peace agreements with Israel.
Israel and its ally the United States don't want Abbas to agree to a coalition unless Hamas meets Western demands to recognize Israel and renounce violence.
But Saudi Arabia sees the revival of the Israeli-Arab peace process as vital to calming the Mideast.
"What's going on in the land of Palestine serves only the enemies of the Islamic nation," the king told Abbas on Tuesday, according to the Saudi News Agency.
In Jerusalem, meanwhile, Israeli Prime Minister Ehud Olmert said he would be meeting with Abbas and U.S. Secretary of State Condoleezza Rice on Feb. 19.
"I hope that by then we will not find that Abu Mazen (Abbas) has partnered with Hamas in a way that is in contradiction of the principles of the quartet and the international community," he said.
With files from The Associated Press
