Flags fly outside the United Nations headquarters during the 74th session of the United Nations General Assembly
FILE - Flags fly outside the United Nations headquarters during the 74th session of the United Nations General Assembly, Sept. 28, 2019.

NEW YORK - The U.S. ambassador to the United Nations reassured Congress Wednesday that she is working to monitor and rein in what she called China's "malign influence" at the world body. 

"China has been aggressive and coercive in using its power at the United Nations," Ambassador Linda Thomas-Greenfield told the House Foreign Affairs Committee. 

She said Beijing promotes an "authoritarian approach to multilateralism."  

The ambassador pointed to an array of actions, including its influence at three U.N. technical organizations where their nationals are in charge, and Beijing's use of COVID-19 vaccine diplomacy to pressure some poorer nations. 

"We will be pushing hard against those efforts," she said. 

U.S. Ambassador to the United Nations Linda Thomas-Greenfield testifies to the House Foreign Affairs Committee on the Biden administration's priorities for engagement with the United Nations on Capitol Hill in Washington, June 16, 2021.

She urged lawmakers to invest in the United Nations to restore U.S. influence there, which declined during the Trump administration. 

"Our adversaries and competitors are investing in the United Nations. We can't expect to compete unless we do, too," Thomas-Greenfield said. 

More than 40 legislators questioned the veteran diplomat over more than four hours during a hearing on the Biden administration's priorities for engagement with the United Nations. Many expressed concerns about China's persecution of minority Uyghur Muslims in the autonomous Xinjiang province. 

Human rights groups accuse China of sending more than a million Uyghurs to detention camps. China says the compounds are "vocational education centers" intended to stop the spread of religious extremism and terrorist attacks.  

U.S. Representative Michael McCaul asked Thomas-Greenfield if she agrees with the committee that the Chinese government is carrying out a genocide and crimes against humanity on the Uyghurs. 

FILE - A perimeter fence is constructed around what is officially known as a vocational skills education center in Dabancheng in Xinjiang Uighur Autonomous Region, China, Sept. 4, 2018.

"Yes, genocide is being committed against Uyghurs in Xinjiang," she said. "And the PRC government is committing crimes against humanity. We have called the Chinese out on this." 

Lawmakers also expressed concern about China's sway over the World Health Organization, some charging that Beijing's influence had made the WHO fail in its duty to warn the world of the severity of the coronavirus pandemic. 

Thomas-Greenfield made clear that the Biden administration supports "a robust and transparent" investigation into the origins of the pandemic. As for the WHO, she noted it has appointed an independent committee headed by former Liberian President Ellen Johnson-Sirleaf and former New Zealand Prime Minister Helen Clark to review WHO's response. 

"I am confident in their abilities to get to the bottom of this, and I know they are working hard," she said. "Their reputations are attached to this, and we are looking forward to seeing the results." 

U.S. Representative Mark Green asked if Taiwan should participate at the United Nations. China has used its influence over the years to prevent its recognition. 

"We support Taiwan," she said. "We want to see Taiwan recognized for the extraordinary democracy that it is." 

Thomas-Greenfield said the U.S. continues to push at the U.N. for Taiwan's participation in programs that do not require member state status, such as the recent World Health Assembly. However, that effort failed. 

Thomas-Greenfield took up her post as U.N. ambassador and a member of President Joe Biden's Cabinet in February. The posting is the culmination of a wide-ranging, 35-year State Department career.