Palestinian President Mahmud Abbas and Hamas supremo Khaled Meshaal were to meet on Wednesday in the Muslim holy city of Mecca for a crisis summit aimed at ending a deadly power struggle.
They held a brief meeting on Tuesday in Jeddah to lay the groundwork for the summit after they had separately met with Saudi King Abdullah, who is facilitating Wednesday's crucial get-together.
A Palestinian official close to the talks said the Mecca summit would begin early in the afternoon.
Abbas was the first to arrive on Tuesday in the Red Sea city of Jeddah and went straight into talks with the king, who had invited the rival leaders to meet in the kingdom to end their differences.
Meshaal and Hamas prime minister Ismail Haniya arrived soon after and later met with the monarch, officials said.
The Mecca summit will seek to overcome deep-seated differences between the rival factions on a power-sharing agreement, a national unity government and ties to Israel.
King Abdullah said he wanted the meeting to lead to a resolution of the inter-Palestinian fighting.
"I hope that the brothers will not leave the holy place without an agreement ... And that they will swear ... To stop this bloodshed," he was quoted by the official news agency SPA as saying.
"That which is happening on the ground (in the Gaza Strip) serves only the enemies of the Arab-Islamic nation and, if it continues, it will deprive the Palestinian people of the fruits of their long heroic struggle to recover their national rights," the monarch said during his talks with Abbas.