Those taking part in a two-day referendum for a constitution Moussa helped draft as chairman of a 50-member committee expressed overwhelming support for the measure.
Moussa, a former presidential candidate and secretary-general for the Arab League, said in an interview published Thursday by pan-Arab daily newspaper Asharq al-Awsat he would stand behind the ruling general if he decided to run as a civilian candidate in eventual elections.
"I believe that Sisi will take this decision [to stand for president] and I back this," he said. "This [Sisi running for presidency] is a very normal scenario, and he must stand."
Sisi assumed power when the military removed Mohamed Morsi from power in July. Morsi, now in jail, was elected president as a candidate from the now-banned Muslim Brotherhood's political wing in Egypt's first-ever democratic election in 2012.
Morsi replaced Hosni Mubarak, a former military officer who resigned during Egypt's revolution in 2011.
The Muslim Brotherhood, which called for a boycott of the two-day referendum, said Sisi's takeover was a military coup.