NEW YORK (REUTERS) - US President-elect Joe Biden's pick to be his ambassador to the United Nations in New York will have to tackle Washington's waning leadership at the world body in the face of a more assertive China, diplomats and analysts said on Monday (Nov 23).

Mr Biden nominated veteran US diplomat Linda Thomas-Greenfield and restored the post to a Cabinet role. If confirmed by the US Senate, Ms Thomas-Greenfield would succeed President Donald Trump's two UN envoys - first Ms Nikki Haley, who was in the Cabinet and later Ms Kelly Craft, who was not. Both had little foreign policy experience before taking up the role.

Ms Thomas-Greenfield is a 35-year veteran of the US Foreign Service who has served on four continents, perhaps most notably in Africa.

"My mother taught me to lead with the power of kindness and compassion to make the world a better place. I've carried that lesson with me throughout my career in Foreign Service - and, if confirmed, will do the same as Ambassador to the United Nations," Ms Thomas-Greenfield tweeted on Monday.

Ms Thomas-Greenfield, who is Black, described last year how that approach helped her when she was a US diplomat in Rwanda during the April 1994 genocide and faced a "glazed-eyed young man" who had mistaken her for a woman that he had been sent to kill.

"I looked that young man in the eye and I asked him his name. And I told him mine. ... If he killed me, I wanted him to know the name of the person he'd killed," she said during a presentation. "I used the power of kindness and compassion and I would survive."

Ms Thomas-Greenfield served most recently as the assistant secretary of state for Africa during President Barack Obama's administration, leading US policy toward sub-Saharan Africa during tumultuous events such as the West Africa Ebola outbreak.

'Grinding work'

If confirmed, she would join counterparts with decades of experience in international diplomacy from Britain, France, China and Russia - which along with the United States - make up the UN Security Council's permanent five veto-wielding members.

"The billion-dollar question hanging over the US at the UN is if Thomas-Greenfield can contain China's rising influence in the organisation, which Trump's slash-and-burn approach to multilateralism has signally failed to do," said Mr Richard Gowan, International Crisis Group UN director.

"That will involve a lot of grinding work to increase trust with non-Western diplomats," he said.

Beijing has been pushing for greater multilateral influence in a challenge to traditional US leadership and tensions between the two superpowers have hit a boiling point at the United Nations over the deadly coronavirus pandemic.

China and the United States "working together to promote a bigger role of the UN in addressing global challenges is not only what the world wants but also in the common interests of the two countries," a Chinese diplomat, speaking on condition of anonymity, told Reuters on Monday.

Trump's wariness of multilateralism also saw the United States announce plans to quit the World Health Organisation, pull out of the UN Human Rights Council, the UN cultural agency Unesco and a global accord to tackle climate change.

Mr Jeffrey Feltman, a veteran US diplomat who was UN political affairs chief from 2012 to 2018, described Ms Thomas-Greenfield as "tailor-made for the type of diplomacy we need today to restore US leadership and rebuild multilateral alliances to meet today's global challenges."

UN diplomats broadly welcomed Mr Biden's announcement.

"A woman of colour, a woman of substance and a woman of experience. She will be a tremendous asset to the UN and a partner for all of us, I am sure," said a senior Asian diplomat, speaking on condition of anonymity.

A senior Gulf diplomat, also speaking on condition of anonymity, said Ms Thomas-Greenfield's appointment was a "strong and welcome signal of the incoming administration's commitment to the UN and to multilateralism."

"Active American leadership is particularly important now as the world faces a range of transnational challenges like Covid, economic shocks and climate change," the diplomat said.