President Barack Obama congratulated French president-electFrancois Hollande for his victory Sunday, but warned of "challenges" ahead, a clear reference to Afghanistan and eurozone debt crisis.

The US president was among the first world leaders to welcomeHollande's election as France's first Socialist president in nearly two decades, a result sure to have major implications for Europe as it struggles to emerge from a financial crisis.

Obama invited Hollande for bilateral talks at the White House later this month ahead of a G8 leaders meeting he will host at his Camp David retreat in Maryland between May 18-19, and a NATO transatlantic alliance summit in Chicago on May 20-21.

In a telephone call, Obama "indicated that he looks forward to working closely with Mr Hollande and his government on a range of shared economic and security challenges," White House spokesman Jay Carney said in a statement.

Among the thorny issues the two leaders will have to address is the eurozone debt crisis, which Washington sees as a threat to its still-halting recovery after a grueling recession. Unemployment, which stood at five percent in early 2008, is now at 8.1 percent -- high for the United States.

Hollande says he wants to renegotiate the European Union's fiscal pact in order to complement its austerity rules with more targeted investment in jobs and growth.

His position stands in sharp contrast to that of Germany's Angela Merkel, the arch-defender of the austerity rules and deficit-cutting targets embedded in the fiscal pact.

But it echoes Obama's support for both growth and economic stability in Europe.

"If Europe is growing, then that benefits the US economy as well," Obama said in February.

At the NATO summit, leaders are due to discuss NATO's carefully crafted plan to hand security control to Afghans by 2014.

Hollande has pledged to start bringing 3,300 French soldiers home this year, ending his country's combat role two years earlier than NATO. He now has to work hard to reassure allies in the transatlantic military alliance that his plan will not upend the war strategy.

The early French pull-out challenges NATO assurances that there would be no "rush to the exit" in Afghanistan, even though the war is unpopular in the West after a decade of fighting that has killed almost 3,000 foreign troops and has yet to defeat the Taliban despite the presence of 130,000 foreign troops.

During their conversation, Obama and Hollande "each reaffirmed the important and enduring alliance between the people of the United States and France," the White House said.

But the statement did not mention outgoing French President Nicolas Sarkozy, with whom Obama has had warm ties during the more than three years they were both in office. Obama is fighting for a reelection bid in November elections.