"With great pain, we received the sad news of the death of the great architect Cesar Pelli," he wrote in his Twitter.
Mansour expressed his condolences to the family, friends and relatives of the architect.
One of the most famous architectural buildings built by Pelli is the Petronas Towers in Kuala Lumpur, as well as the buildings of the World Financial Center in New York.
In May, the death of American architect Bei Yuming was reported.