Mohamed Selim al-Awa, 70, is one of the three main Islamists bidding for the top job in Egypt's first presidential election since the ouster of Hosni Mubarak in a popular uprising in February 2011.
He warned the Muslim Brotherhood against putting up their own candidate, saying such a move would suggest that the group with the biggest bloc in parliament wanted to monopolise power, which could harm Egypt's image abroad.
Nominations for the presidential race will be finalised in April and voting starts in May. The strongest candidates to emerge so far are either Islamists or those with links to Mubarak's era.
Awa, seen by many as a moderate Islamist and the former secretary-general of the well-respected International Federation of Islamic Scholars, is the third favourite among Islamists. Non-Islamist rivals include Amr Moussa, a former head of the Arab League and ex-foreign minister under Mubarak, and Ahmed Shafiq, a former air force commander.
"Before the election, by a day or two or even a week, it would be wise and rational that every political stream has one candidate," Awa told Reuters in an interview from the Cairo offices of his law practice.
"I expect this to happen," he said, adding that the alternative was "huge vote fragmentation".
Awa's rivals in the Islamist camp include Hazem Salah Abu Ismail, who follows the ultraconservative Salafi school of Islam, and Abdel Moneim Abol Fotoh, who had been a member of the Brotherhood until he was kicked out for seeking to run.
The Brotherhood had said it would not field its own candidate and would back one of the hopefuls on the list. However, officials say the group may change its mind if it does not find a candidate to support.
"If a candidate comes from the Brotherhood ... the local situation will get complicated as people will think the Islamic stream has seized the country," said Awa.
"There must be some differences between the president and the parliament majority or else the president will be confined by parliament," he said.
The Muslim Brotherhood's Freedom and Justice Party (FJP) and Salafi al-Nour Party claimed more than 70 percent of parliament's seats, making their support of a candidate "very influential", Awa noted.
He argued that Egypt - a country of 80 million people, 90 percent of them Muslims - should have an Islamist leader and said people would back a candidate who "convinced (them) about his religious thought and practice".
A number of Islamist figures and institutions have called on the Islamist candidates to strike a deal for just one of them to run. Awa said he has accepted three invitations by Islamic groups for talks but said his Islamist rivals had not responded.