Lebanese President Michel Aoun has refused to accept the resignation until Hariri returns to present it in person.
Hariri's sudden resignation on November 4 thrust Lebanon to the forefront of regional tussle between the Sunni monarchy of Saudi Arabia and Shi'ite Islamist Iran, whose powerful Lebanese ally Hezbollah is part of the government.
Hariri's arrival in Cairo coincided with the arrival of the Egyptian president from a two-day visit to Cyprus where he attended a tripartite summit with Greece.
El-Sisi also highlighted his country's "full support for preserving Lebanon's stability".
Saad Hariri had unexpectedly resigned as Prime Minister from Saudi Arabia resulting in a political crisis in the region. He said that he will celebrate Lebanon's Independence Day on Wednesday, adding he would clarify his political position when he returns to Lebanon. Hariri is now in Paris, where he met French President Emmanuel Macron on Saturday.More news: What Does Net Neutrality Rollback Mean For You?
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"Saad Hariri arrived in Cairo on Tuesday evening from Paris to meet President Sisi, and he is scheduled to return to Lebanon on Wednesday", MENA state news agency said.
His father, late Prime Minister Rafik al-Hariri, was assassinated in 2005 and an global court is still investigating the tragedy.
Hariri and Sisi agreed on the necessity for Lebanon to be disassociated from any regional issues and the Lebanese outgoing prime minister praised Sisi for his keenness on maintaining Lebanon's stability, according to Hariri's remarks following the meeting.
Al-Hariri's resignation has not yet been approved by Lebanon's president.