CAIRO, 9 (Reuters) - Former Egyptian Prime Minister Ahmed Shafiq says he will back army chief General Abdel Fattah al-Sisi for president in an election expected next year, adding to speculation that the man who led the overthrow of President Mohamed Mursi could become head of state.

Shafiq, a former air force commander who came second in last year's presidential election, said he would not run if Sisi did.

The comment suggests why, just months before the election, there are no declared candidates as politicians wait to see if Sisi is going to run before announcing their own intentions.

Sisi has said he does not seek authority though speculation he will run has mounted since he toppled the Muslim Brotherhood's Mursi from the presidency on July 3. Sisi is widely expected to win if he runs.

In an interview with Dream 2 television station, Shafiq said he would run for president if he had broad support but he would not contest an election if Sisi did.

"May God give him good fortune. We would all support him and I am the first one to support him," said Shafiq, who came second to Mursi in the presidential election in 2012. "If Sisi is nominated I will not run."

Shafiq was one of an array of candidates who ran in last year's election, the first time Egyptians freely chose their head of state. The vote was preceded by months of frenzied campaigning, in stark contrast to now.

Even if Sisi does not run, analysts say the military will remain at the heart of power, curbing the influence of the next head of state.

Hamdeen Sabahi, a leftist politician who came third in the 2012 election, has also said Sisi would win, while sidestepping questions on his own intentions.

Analysts have suggested retired or serving military officers would run. Sisi was head of military intelligence under Hosni Mubarak. Former Arab League chief Amr Moussa, who came fifth in the election, is also seen as a possible contender.

The Brotherhood has accused Sisi of trying to rehabilitate the old order that ran Egypt for 30 years under Mubarak.

Sisi has emerged as the public face of the new order, enjoying fawning coverage in Egyptian media and sowing doubts about the military's promise to hand over to full civilian rule with a "road map" to parliamentary and presidential elections.

The army-backed interim government, with the support of a sizeable section of the population, has been cracking down hard on the Muslim Brotherhood, a million-member movement that emerged from decades of repression under Mubarak's military-backed rule to win five popular votes in all.

More than 2,000 Islamist activists have been arrested since Mursi was ousted and most of the Brotherhood's top leaders, including Mursi, have been jailed on charges of inciting or taking part in violence. Some have also been accused of terrorism or murder.

Over the same period, more than 1,000 people have been killed in political violence. Most were protesters killed by security forces breaking up pro-Mursi camps in Cairo. Abound 100 were members of the security forces. (Reporting by Michael Georgy; Editing by Angus MacSwan)