German Chancellor Angela Merkel said Sunday, November 20 she would seek a fourth term in elections next year to defend democratic principles in the face of looming threats at home and abroad, AFP reports.

Predicting her toughest campaign to date, Merkel said the forces of populism as well as the uncertainty created by poll triumphs for Brexit and Donald Trump meant she had a "duty to serve my country."

"We are facing struggles in Europe and internationally for our values and our interests and, simply put, for our way of life," Merkel, 62, told reporters at the headquarters of her Christian Democratic Union (CDU) party.

"This election will be more difficult than any before it, at least not since national reunification" in 1990, she added, citing a strong "polarisation of our society".

Merkel, the EU's longest serving leader, said she had "endlessly" weighed her choice and knew that in "distinctly difficult, even insecure times", many leaders were looking to her as a source of stability.

"I am indeed honoured but I also find it grotesque and even absurd" that some commentators have suggested she should be considered the new "leader of the free world", she said.

Speaking to German television channel ARD, she vowed to seek a "strong Europe" after Britain voted to leave the bloc.

Merkel ended months of feverish speculation earlier by telling CDU leaders that she would stand again, a decision they welcomed with "thunderous applause," party sources told AFP.

She has governed Europe's top economic power, which does not have term limits, since 2005.

Another full four-year mandate, which pollsters say she is likely to win, would tie the post-war record set by her mentor Helmut Kohl, who presided over the 1989 fall of the Berlin Wall.