French President Francois Hollande speaks at a press conference in Paris, France, June 24, 2016. (Xinhua/Theo Duval)

PARIS, Nov. 9 (Xinhua) -- French President Francois Hollande on Wednesday congratulated Donald Trump on his victory in the U.S. presidential election, but warned that the American vote would open a period of uncertainty.

"I congratulate him as is natural between two democratic heads of state," said Hollande.

However, he warned "This American election opens a period of uncertainty,"that showed the necessity of "strong France," and "a united Europe, capable of making itself heard and of promoting policies wherever its interests or its values are challenged."

In a televised address, the French president said France would be frank and vigilant in talks with the new American administration as "what is at stake is peace, the fight against terrorism, the situation in the Middle East, the economic relations and the preservation of the planet."

As French presidential election is approaching in a context of growing public disenchantment, Hollande said the United States mirrored "concerns that are provoked by the world's disorders."

"We have find the answers which must be able to overcome fears but also respect the principles ... of democracy and the social model," he stressed.

Former real estate tycoon Trump has been elected the 45th president of the United States after defeating his Democratic rival Hilary Clinton.

During his campaign, he drew controversy due to his harsh tone on immigration. He also pledged to undo a global deal on climate change accord agreed in Paris last year and renegotiate a deal between World leaders and Iran on nuclear program.