Soleiman Awad, the spokesman of the Egyptian president, said on Wednesday that President Hosni Mubarak and King Abdullah of Saudi Arabia had agreed at a meeting on Tuesday that the probe should work "to unveil the truth on the assassination ... in keeping with international law".
They also agreed during their talks in the Red Sea city of Jeddah that "the cooperation of Damascus with the international commission of inquiry is necessary to avoid any harm" to Syria, he was quoted by Al-Ahram daily as saying.
The two leaders also underlined "the need to preserve the historic links between Lebanon and Syria".
Later on Wednesday, Mubarak was due to meet Jacques Chirac, the president of France, in Paris for talks focused on Syria, which has come under mounting pressure over last February's assassination of al-Hariri in a Beirut bomb blast.
Al-Ahram said Mubarak's consultations with King Abdullah and Chirac were part of his "regional and international actions to save the situation in Syria and Lebanon".
Abdel Halim Khaddam, a former vice-president of Syria who is now living in Paris, said last week that Bashar al-Assad, the Syrian president, had threatened al-Hariri months before the assassination.