Francois Hollande was sworn in as France's first Socialist president since 1995 on Tuesday at a solemn ceremony overshadowed by the debt crisis threatening to unravel the eurozone.
After brief ceremonies in Paris, the 57-year-old career politician was to dash to Berlin to confront Chancellor Angela Merkel over their very different visions as to how to save the single currency bloc.
"Power will be exercised at the summit of the state with dignity and simplicity," Hollande declared in an inaugural address to Socialist leaders, trade unionists, military officers, churchmen and officials.
"Europe needs plans. It needs solidarity. It needs growth," he said, renewing his vow to turn the page on austerity and invest for the future, and implicitly underlining his differences with Merkel.
"To our partners I will propose a new pact that links a necessary reduction in public debt with indispensable economic stimulus," he said.
"And I will tell them of our continent's need in such an unstable world to protect not only its values but its interests."
Hollande was also to make the much-anticipated announcement of who will lead his government as prime minister, with Jean-Marc Ayrault, the head of the Socialists' parliamentary bloc, tipped as favourite.
The new president was welcomed to the Elysee Palace by his predecessor Nicolas Sarkozy, who led him to the presidential office for a private head-to-head and to hand over the codes to France's nuclear arsenal.
Then Hollande ushered Sarkozy to his car for a final farewell, outgoing first lady Carla Bruni exchanging kisses with successor Hollande's partner Valerie Trierweiler, elegant in a dark dress and vertiginous heels.
Hollande then signed the notice of formal handover of power and headed back in to the palace ballroom.
No foreign heads of state were invited to what was a low-key ceremony for a post of such importance, leader of the world's fifth great power.
After the swearing in, Hollande rode up the Champs Elysees to the Arc de Triomphe in an open-topped Citroen DS5 hybrid, waving to the crowd.
But the real work was to begin later in the afternoon, when Hollande was to fly to Berlin from an airbase north of Paris, for tense talks with Merkel, the leader of Europe's biggest economy and France's key ally.
Merkel was a Sarkozy ally and the architect of the European Union's fiscal austerity drive. Hollande opposed the speed and depth of the cutbacks demanded by Berlin, and wants to renegotiate the eurozone fiscal pact.
Germany is committed to budgetary discipline, and Merkel has repeatedly insisted since Hollande's election that the pact, signed by 25 of the 27 EU countries and already ratified in some, is not open to renegotiation.
But observers say there is room for compromise, with Hollande likely to agree to additional stimulus measures without a rewrite of the pact.
And with political paralysis in Greece raising the spectre of the country being forced from the eurozone, the heads of Europe's two largest economies will be keen to reassure worried markets they can work together.
New figures released Tuesday showed France's economy still stagnant, with official statistics agency INSEE saying it recorded no growth in the first quarter of 2012.
The agency also revised downward the growth figure for the fourth quarter of 2011, to 0.1% from 0.2%, while maintaining that the economy grew by 1.7 percent overall in 2011.
Before he heads to Berlin, Hollande's first order of business will be to nominate a prime minister, who will be tasked with forming a government before a first cabinet session likely on Thursday.
Ayrault, a 62-year-old longtime Hollande ally, is considered first in line for the job, but other names are circulating.
Once the cabinet is named, the focus will move to the Socialists' campaign to win a parliamentary majority in June's legislative elections -- a key test for the party after Hollande's win.
After the talks with Merkel, Hollande heads to the United States where he is to meet President Barack Obama at the White House on Friday ahead of back-to-back G8 then NATO summits.