"I mourn with deep sorrow and grief one of the most precious men and one of the greatest leaders, Khalifa bin Zayed Al Nahyan, the president of the UAE, who passed away after a long journey of giving," the Egyptian president wrote on his social media accounts Friday.

El-Sisi added that the UAE's late president "gave much to his country and his nation until the Emirates became an icon for development and modernity in our region and the world."

"In my name and the name of the Egyptian people, I offer my condolences to the Emirati leadership, state and people in this great loss."

"I pray to Allah Almighty to extend his mercy and forgiveness to the late UAE president and to maintain the UAE's progress and pride," added El-Sisi.

The UAE announced a 40-day mourning period nationwide starting Friday over the death of the long-time ruler.

Sheikh Khalifa bin Zayed Al-Nahyan served as the second president of the UAE and the 16th ruler of Abu Dhabi since 2004.