Paris (AFP) - Former interior minister Bernard Cazeneuve took over as French prime minister on Tuesday, replacing Manuel Valls who has resigned to fight for the Socialist party nomination in presidential elections next year.
Valls, 54, stepped down after two and half years in office marked by a string of terror attacks, the trauma of which he said "will never leave us."
He acknowledged that his desire to run for president next year made it "impossible for me to be a candidate and prime minister at the same time" before hinting at the difficult challenges ahead.
"I understand what I have to do before the French people," he said at the prime minister's residence in central Paris where Cazeneuve was sworn in for what is expected to be a short stint in office.
Cazeneuve, 53, will essentially be a caretaker for the final six months of President Francois Hollande's troubled term in office which will end after elections in May.
Hollande, who has the worst approval ratings in nearly 60 years, has decided not to seek re-election to give his beleaguered and divided party a chance in next year's vote.
Cazeneuve insisted that "each day counts" as he pledged to work to keep France safe from the "extremely high" terror threat which he witnessed firsthand as interior minister since April 2014.
The promotion of the widely-respected austere former lawyer has led to a minor reshuffle in the cabinet, with Bruno Le Roux, leader of the Socialists in the lower house of parliament, promoted to interior minister.
- Valls under attack -
Spanish-born Valls, a centrist and pro-business moderniser, will now throw himself into campaigning for the Socialist party nomination against his more left-wing rivals.
Appealing to the party to unite, Valls declared his bid on Monday evening, saying he wanted to challenge election frontrunner Francois Fillon, from the rightwing Republicans party, as well as far-right National Front (FN) leader Marine Le Pen.
"We're told that Francois Fillon is the next president of the Republic. Nothing is set in stone," Valls said from the multicultural Parisian suburb of Evry.
But the twice-married football fan has alienated many in the Socialist party during his time in office and he will also need to escape the shadow of Hollande with the wider French public.
Polls currently place him fifth in the election next year if he clinches his party's nomination -- a humiliation for the Socialists which have been France's main leftwing force since World War II.
Le Pen and Fillon are far out in front in the opening round of the election on April 23, with Fillon expected to beat Le Pen in May's second round, surveys show.
Valls would crash out with 10 percent if he won the Socialist nomination -- behind former economy minister Emmanuel Macron and the Communist-backed Jean-Luc Melenchon, an Ifop-Fiducial poll showed Tuesday.
He will go up against seven other candidates in the two-round Socialist party primary on January 22 and 29, including former more leftist cabinet colleagues Arnaud Montebourg and Benoit Hamon.
"His intentions as a candidate are contradicted by his acts as prime minister," Hamon said on Tuesday. "His candidacy is without doubt the most divisive there is today in the Socialist party."
The charges against Valls include his use of decrees to force through labour reforms and his call for dual-national terror convicts to be stripped of their French nationality.
His stern line on secularism and Islam has also turned off many lifelong Socialists after he declared the Islamic burkini swimsuit was "not compatible" with French values over the summer.