Joe Biden's UN pick to warn that US absence allows China to thrive at world body

US President Joe Biden's nominee to be ambassador to the United Nations will stress on Wednesday the importance of US re-engagement with the 193-member world body in order to challenge efforts by China to "drive an authoritarian agenda."

Veteran diplomat Linda Thomas-Greenfield is due to appear before the Senate Foreign Relations Committee for her confirmation hearing. She is a 35-year veteran of the US Foreign Service who has served on four continents, most notably in Africa.

"We know China is working across the UN system to drive an authoritarian agenda that stands in opposition to the founding values of the institution - American values," Thomas-Greenfield will say, according to excerpts from her statement.

"Their success depends on our continued withdrawal. That will not happen on my watch," she will say.

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

Former President Donald Trump was critical of the United Nations and wary of the value of multilateralism. He announced plans to quit the World Health Organization (WHO), and pulled out of the UN Human Rights Council, the UN cultural agency UNESCO, a global climate change accord and the Iran nuclear deal.

On his first day in office last week, Biden rescinded the US decision to withdraw from the WHO and announced a return to the climate agreement.

"When America shows up, when we are consistent and persistent, when we exert our influence in accordance with our values, the United Nations can be an indispensable institution for advancing peace, security, and our collective well-being," Thomas-Greenfield will say.

"If instead we walk away from the table, and allow others to fill the void, the global community suffers — and so do American interests," she will say.

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