By David Lawder and Kanishka Singh WASHINGTON (Reuters) - The United States is working hard to counter China's influence in international institutions and in lending to developing countries, U.S. Treasury Secretary Janet Yellen said on Wednesday. Yellen said she was concerned by some of China's activities globally, particularly in lending to developing countries. I am very very concerned about some of the activities that China engages in globally, engaging in countries in ways that leave them trapped in debt and don't promote economic development, she said in a hearing before the State, Foreign Operations, and Related Programs subcommittee of the House Appropriations Committee. China spent $240 billion bailing out 22 developing countries between 2008 and 2021, with the amount soaring in recent years as more have struggled to repay loans spent building Belt and Road infrastructure, a recently published study showed. Almost 80% of the lending was made between 2016 and 2021, mainly to middle-income countries including Argentina, Mongolia and Pakistan, according to the report by researchers from the World Bank, Harvard Kennedy School, AidData and the Kiel Institute for the World Economy. China has lent hundreds of billions of dollars to build infrastructure in developing countries, but lending has tailed off since 2016 as many projects have failed to pay the expected financial dividends. China is negotiating debt restructurings with countries including Zambia, Ghana and Sri Lanka and has been criticised for holding up the processes. In response, it has called on the World Bank and International Monetary Fund to also offer debt relief. The Chinese government has hit back at its critics by saying its overseas investments operated on the principle of openness and transparency . (Reporting by David Lawder, writing by Kanishka Singh; Editing by Marguerita Choy)