American universities hosting Chinese-backed Confucius Institutes need to make public the details of their arrangements, including the amount of money they receive from the organization, according to regional experts.

Though Beijing bills the Confucius Institutes as a center to promote Chinese language education and cultural exchange around the world, there are mounting concerns in the United States that they threaten academic freedom, in part by limiting discussion on issues sensitive to the Chinese government.

"One of the features of the Confucius Institutes that's now aroused the greatest concern is that they in many cases involved secret covenants between funders and the host institutions, or universities, that were not made public," Aaron Friedberg, a professor of politics and international affairs at Princeton University, told the House Armed Services Committee on Thursday.

More than 100 Confucius Institutes have opened at American universities in the past 13 years, but little is known about the nature of those agreements and the dollar-amounts invested in U.S. college campuses. Public universities have faced severe funding cuts over the past decade, making it attractive for cash-strapped institutes to outsource Chinese classes or programs to Confucius Institutes footing the bill.

Rep. Joe Wilson (R., S.C.) likened the project to a "propaganda operation." The Chinese government has said as much itself. In 2009, Li Changchun, then head of propaganda for the Chinese Communist Party, described the Confucius Institutes as "an important part of China's overseas propaganda setup."

FBI Director Christopher Wray told the Senate Intelligence Committee on Tuesday that the bureau is investigating dozens of Confucius Institutes across the United States amid concerns they are part of covert intelligence and influence operations.

"They appear benign, and I suppose in some sense some of their activities might be, but they have this tie to the Chinese regime," Friedberg told House members. "They've also allegedly in a number of instances played a role in shaping discussion on college campuses and elsewhere of issues related to China and suppressing the expression of some views that the Chinese regime finds offensive."

A 2014 pamphlet published by retired University of Chicago anthropologist, Marshall Sahlins, said that Confucius Institute instructors are barred from discussing human rights in China or the Tiananmen Square massacre, Politico reported. When asked about the political status of Tibet, an autonomous region of China, instructors are directed to refocus the discussion to an unrelated topic, such as Tibet's indigenous cultural practices.

Ely Ratner, a senior fellow for China studies at the Council on Foreign Relations, recommended that American universities setup association groups to establish standards of behavior or shared norms on how they will accept Chinese money to limit backdoor competition over these funds.

"If there were standards of transparency and everybody was operating at the same level that would create a fair playing field and not lead to some of these more secret, private, malicious agreements," Ratner told the House panel.