UNITED NATIONS, United States — The UN General Assembly has  appointed Antonio Guterres as the new secretary-general of the United Nations, in a shift towards a more high-profile leadership of the world body.

The former prime minister of Portugal pledged to work as a "bridge-builder" and "honest broker" after the 193 member-states unanimously named him to be the world’s diplomat-in-chief beginning January 1.

The socialist politician, who also served as UN refugee chief for a decade, is expected to play a more prominent role at the helm than Ban Ki-moon, the South Korean who will step down after two five-year terms.

Guterres was greeted by loud applause as he entered the packed hall following the vote and told the assembly he was "fully aware of the challenges the UN faces and the limitations of the secretary-general."

"The dramatic problems of today’s complex world can only inspire a humble approach," he said, adding that the UN chief "alone neither has all the answers, nor seeks to impose his views."

US President Barack Obama congratulated Guterres, saying in a statement that "he had the character, vision and skills needed to lead the United Nations at this critical moment."

Russian President Vladimir Putin telephoned Guterres from the Kremlin and wished him success "in this important and demanding position."

French President Francois Hollande said "the world more than ever needs a strong United Nations" and praised Guterres for his demonstrated ability to "set a course of action, show leadership and enact reforms."

The appointment of the 67-year-old polyglot comes at a time of global anxiety over the ongoing war in Syria, the refugee crisis and raging conflicts in South Sudan and Yemen.

On Syria, the most pressing crisis on the UN agenda, Guterres said it was time for world powers to overcome divisions about ending the war, just as key players were gearing up for a new round of talks at the weekend. 

"Whatever divisions might exist, now it’s more important to unite," Guterres told reporters after the vote. "It’s high time to fight for peace."

The United States and Russia will be joined by regional heavyweights for talks in Lausanne on Saturday, and Washington will then meet with its European partners on Sunday.

The Security Council is deadlocked over Syria after two draft resolutions were defeated in separate votes -- one of them vetoed by Damascus ally Russia.

 Guterres, the first former head of government to become UN chief, called for determined action to confront terror groups and populists who "reinforce each other" in their extremism.

"We must make sure that we are able to break these alliances between all those terrorist groups or violent extremists on one side, and the expression of populism and xenophobia on the other side," he said.

The remarks were apparently directed at European far-right politicians and also US presidential contender Donald Trump, whose anti-immigrant rhetoric has caused global concern.

Citing Guterres’ political and UN experience, US Ambassador Samantha Power said he brings "both head and heart" to what has been described as the most impossible job in the world.

"We have selected a candidate who is prepared to cut past the jargon and the acronyms, and the sterile briefings, and get real," she said.

"He knows the only measure of our work here is whether we are or are not helping and supporting real people."

Guterres last week won the unanimous backing from the Security Council to take the helm of the United Nations, capping a campaign that saw 13 candidates run for the top post including, for the first time, seven women.

The incoming UN chief has pledged to make gender parity a priority of his reforms during his five-year term at the world body.

Women currently only make up 25 percent of senior leadership posts at the United Nations and there had been calls during the campaign for the first woman to be elected secretary-general, after eight men in the job. — AFP