Nicolas Sarkozy has launched a bid to win back the French presidency, announcing he will seek his party's nomination to run in next year's election.
The 61-year-old conservative's plan became apparent on Monday.
"I have decided to be a candidate in the 2017 presidential election," Sarkozy wrote in a new book, Tout pour la France (All for France), due out this week.
"France demands that you give her your all. I feel I have the strength to lead the fight at such a turbulent moment in our history," he wrote in an extract seen by AFP news agency, alluding to the attacks that have rocked the country since January 2015
"The next five years will be filled with danger but also with hope."
In 2012, Sarkozy ended a five-year term mired in unpopularity, had made no secret of his ambition to reconquer the top office.
Sarkozy's aides told AFP he was expected to step down as the leader of the centre-right Republicans to focus on his bid.
Party primaries take place on November 20 and 27.
Sarkozy's first campaign stop will be on Thursday at Chateaurenard, near the southern French city of Avignon.
Sarkozy itemised major challenges in the years ahead, including strengthening respect for "French identity", restoring lost competitiveness and enforcing state authority.
On the economic front, he pledged to reduce payroll charges, scale back unemployment payments for those who have been jobless for more than one year and slash income tax by 10 percent.
On immigration, he proposed "suspending" the right of family members to join a migrating relative in France.
"The big problem with our immigration policy is firstly that of numbers," he said.
Sarkozy's announcement coincides with a resurgent debate on the place of Islam in French society, encapsulated in the row over the Islamic burkini swimsuit.
He said France's "principal battle" was over how "to defend our lifestyle without being tempted to cut ourselves off from the rest of the world".
The opposition leader, who has repeatedly dismissed Socialist President Francois Hollande as weak, said he would also restore authority in neighbourhoods where he said "minorities are successfully blackmailing the current authorities".
Sarkozy was defeated in his bid for re-election in 2012 after conducting a campaign seen by many in his own camp as too right-wing.
|Sarkozy, left, and Hollande are both considered poor leaders of France [Philippe Wojazer/Reuters]
Sarkozy becomes the 13th person to put their name forward for the French presidency, a job that has sweeping powers.
He faces several challengers within conservative ranks.
His chief rival, Alain Juppe, the former premier and Bordeaux mayor, is seen as a moderate and is the favourite to win the party's nod.
But Juppe's lead in opinion polls has shrunk in recent weeks as Sarkozy steps up his rhetoric on conservative Muslims and immigration following the July 14 lorry attack in Nice.
Sarkozy has already won the support of a Republican heavyweight, Christian Estrosi, who is president of the southern region that includes Marseille.
"He is the best candidate," Estrosi told the Journal de Dimanche.
If Sarkozy wins, he could face a rematch against Hollande, who has said he too has the "desire" for a second term.
But opinion polls overwhelmingly show the French wanting neither man as their leader.
Hollande has even surpassed Sarkozy to become the most unpopular president in post-war France.
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Sarkozy would also face far-right National Front leader Marine Le Pen, who is tipped to make it to a second round of voting.
His reputation remains tainted by two major inquiries, into alleged influence-peddling and into suspected illegal funding of his 2012 election campaign.
But true to his famous self-belief, these scandals have failed to dent his ambition of returning to the Elysee Palace.
Hollande, on a trip to southern Italy for talks with German Chancellor Angela Merkel and Matteo Renzi, the Italian prime minister, declined to comment on Sarkozy's bid, or on another challenge for the presidency launched by left-wing Socialist Arnaud Montebourg.