In his first interview with Egyptian TV, he added that two assassination plots against him had been uncovered.
Mr Sisi removed Egypt’s first democratically elected president Mohammed Morsi from power last July.
He is widely expected to win the presidential election on 26-27 May.
Mr Sisi had denied that he had any political ambitions when he ousted the Brotherhood last year.
He said he changed his mind because of threats from both inside and outside Egypt.
“Whoever has an opportunity to come forward to protect this country, and this people and their future, had to come forward” Mr Sisi said.
If he does become president, Mr Sisi will be the latest in a line of Egyptian rulers drawn from the military, going back to the 1950s – a line only briefly broken during President Morsi’s year in office.
Human rights groups say the military-backed authorities have displayed increasing hostility to independent media and to political opponents.
Since Mr Morsi’s overthrow more than 1,000 people have been killed and thousands of members of Mr Morsi’s Muslim Brotherhood been detained by the interim authorities, who have designated the Islamist movement a terrorist group.
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