Amr Moussa said Egypt is going through an economic and social crisis that requires the talents of an experienced statesman, not a president who learns on the job.
Egyptians pick a new president to replace deposed Hosni Mubarak in a process that begins May 23-24. It is unclear how much power the new president will have, as the process for writing a new constitution is snagged over disagreements about makeup of the body that will write the new document.
Moussa served as Egypt's foreign minister under Mubarak and in 2001 moved over to head the Arab League. He resigned that post last year to run for president.
At a news conference Sunday in Cairo, he disagreed with the goals of Islamist parties, which have won clear majorities in parliamentary elections running on a platform of Islamic principles.
"I believe that Egypt has been injured, Egypt has been mismanaged and that Egypt should not get into an experiment that has not been tried before," he said when asked about his top Islamist opponent, a member of Egypt's powerful Muslim Brotherhood.
Such an experiment, he said, could enter Egypt "into a period of confusion."
Critics charge that Moussa's record as a top official under Mubarak could mean his election would mark a return to the ways of the former regime, characterized by corruption, inefficiency and nepotism.
Egypt's economy has been hard hit in the aftermath of the popular uprising. Tourism and investment rates have plummeted, foreign currency reserves have dipped dangerously and the national budget reels under the burden of heavy subsidies on fuel and basic food products.
Thirteen candidates are running to replace Mubarak. Since he resigned after a popular uprising, Egypt's military has been running the country.
Facing Moussa are candidates from the Muslim Brotherhood and other Islamist factions, as well as another Mubarak-era official, Ahmed Shafiq, his last prime minister.
In a last minute decision, the Brotherhood decided to field a candidate in the race, after it had promised it would not. This led many to accuse the Brotherhood of being power hungry, aiming to lead Egypt toward into a religion-based system of government. The Brotherhood says it would have Islam as its reference for governing.
The group's candidate, Mohamed Morsi, said Saturday if he wins, he will be president of all Egyptians, but it is now time to put into practice the group's slogan, "Islam is the solution."
The Brotherhood's main candidate was among 10 disqualified this month by Egypt's election commission, along with another leading Islamist and Mubarak's former intelligence chief, boosting Moussa's chances. Morsi replaced the group's first choice.
Moussa pointed to his credentials as a longtime government official with deep knowledge of the system.
"I believe I can start from minute one as president with my knowledge of the government, the administration, the management and also the connection with the world and the Arab world and the African world, and Europe," he said. "The country is in a major crisis. A major crisis doesn't justify at all a president who will ask around, what should I do at this point or that point and gaining experience as he goes."
The Brotherhood was outlawed for decades before Mubarak was overthrown in February 2011, so its leaders have never held high office.
Moussa, 76, is popular among Egyptians who see in him a seasoned and outspoken diplomat, particularly voicing criticism of Israeli policies.
On the other hand, he has been harshly criticized in recent protest rallies for his association with the Mubarak regime, and many protesters say that he, like other former regime officials, should not be allowed to run in the first post-Mubarak elections.