During a counterterrorism conference in Saudi Arabia, the top Sunni cleric added that the proposed conference should seek to bring about peace among these sects.
"We have to forget about our differences which had brought us nothing but weakness and humiliation," al-Tayeb said.
He said Islamic nations faced what he described as a "neocolonialist" threat posed by international powers.
He added that these international powers sought to divide and rule these Islamic nations, tapping into sectarian tensions within them.
The Grand Imam of Al-Azhar noted that the emergence of Islamist groups that denigrate and vilify other Muslims boiled down to what he described as a "historical accumulation of extremist trends", adding that these trends were based on misguided interpretations of the Quran [the holy book of Muslims] and the sayings of Islam's prophet Muhammad [peace be upon him].
Sunday's conference was sponsored by Saudi Arabia's King Salman bin Abdulaziz.
Top Muslim clerics and security experts showed up at the conference to discuss means of countering rampant terrorism and violence in the name of Islam in the Arab region.