Saudi King Abdullah will meet Egypt's President Abdel Fattah al-Sisi in Cairo on Friday, diplomatic and security sources told AFP, his first visit since the 2011 overthrow of strongman Hosni Mubarak.
Saudi Arabia welcomed the July military ouster of Islamist president Mohamed Morsi led by ex-army chief Sisi and has pledged billions of dollars in aid to Egypt's military-installed authorities.
The king "will stop in Cairo in an unofficial and unannounced visit. It is expected that president Sisi meets him at the (Cairo international) airport", an official from the Saudi embassy in Cairo told AFP on Thursday evening.
An airport security official confirmed the information.
"King Abdullah will visit Cairo and the authorities are taking all necessary measures for Sisi to receive him at the airport or at the Ittihadiya presidential palace", he told AFP.
Sisi won a May 26-28 presidential election after he retired from the army.
King Abdullah hailed his victory and called for a "donors conference" to help Egypt overcome an economic crisis sparked by three years of unrest that followed Mubarak's overthrow.
After Morsi's ouster, Riyadh quickly pledged $5 billion (3.7 billion euros) in aid to Cairo, with Kuwait and the United Arab Emirates offered a combined $7 billion.
Saudi Arabia had long seen Morsi's Muslim Brotherhood as a threat and has declared it a "terrorist" organisation, months after Egypt itself blacklisted the group.
Since Morsi's ouster, a government crackdown on his supporters has left more than 1,400 killed and at least 15,000 jailed.