What the Confucius Institutes do in the United States is visible through the work of those involved, and skeptics can visit the "open and transparent" branches for verification, said Gao Qing, head of the organization that supports 110 such institutes in the US.

Gao, executive director of the Confucius Institute US Center in Washington, made the remarks in light of what he said were recent attempts by some in the US capital to "politicize education matters", which he believes will fail to derail the operations of the Confucius Institutes.

US Senator Marco Rubio warned in a Feb 5 letter of "the Chinese government's increasingly aggressive attempts to use Confucius Institutes and other means to influence foreign academic institutions and critical analysis of China's past history and present policies".

Rubio, a Florida Republican, sent the open letter to a handful of Florida schools in which he said Confucius Institutes (CI) use the teaching of Chinese language and culture as tools to expand the political influence of China.

"The accusation is groundless and doesn't conform to the facts," Gao told China Daily, adding that the fresh wave of criticism against CI coincides with the straining of China-US relations in certain areas, with Washington having designated Beijing a rival.

Rubio, who chairs the Congressional-Executive Commission on China, urged the University of North Florida, the University of South Florida, the University of West Florida, Miami Dade College and Cypress Bay High School to terminate their Confucius Institute agreements.

Gao said that Rubio's request had no impact on the University of West Florida, which decided last fall not to renew its CI agreement when it expires this coming May, citing a lack of student interest.

The University of South Florida, which in 2008 became the first Florida university to host a Confucius Institute, said in response to Rubio that it had found no evidence its CI had been compromised by the Chinese government.

Over the past decade "we have not experienced any effort by the Hanban (the Confucius Institute headquarters in Beijing) to promote certain concepts or principles, and the nature of the partnership presented by our institution to the Hanban at each renewal has not changed," USF System President Judy Genshaft said in a reply letter to Rubio last week.

"The Confucius Institute at USF is in place to help our students and community develop a clearer understanding of Chinese language and culture, but academic authority for all content taught to students belongs exclusively to USF faculty," she said in the letter, which was published in the Tampa Bay Times.

John Delaney, president of the University of North Florida, also said he sees no reason to discontinue the classes offered by the Confucius Institute, whose operation at the UNF campus has prompted no complaints, The Florida Times-Union reported on Feb 6.

"The institutes' two Chinese instructors do not teach political science; they teach Chinese language, and without them, the university would offer fewer Chinese-language courses," the report quoted Delaney as saying.

Juan Mendieta, a spokesman for Miami Dade College, confirmed to China Daily last Thursday that the school has received Rubio's letter and will provide a response "at an appropriate time".

Cypress Bay High School has not yet responded to a request for comment.

In November, Miami Dade College President Eduardo Padrn referred to the institute as "a treasure in our community", reported The Miami Herald on Feb 6. The report said Rubio, who is from Miami-Dade County, has strong ties to the college; Bernie Navarro, who served as finance chairman for Rubio's 2016 presidential and Senate campaigns, is a college trustee.

Gao suggested Rubio listen to how voters in the county perceive the Confucius Institute's contribution to his constituency.

"The Confucius Institute has expanded educational opportunities through language education and increased international exposure through cultural events, which are unavailable otherwise in Florida's underserved communities, especially in Miami," Gao said. About 18 percent of the county's residents live below the poverty line, according to the latest US Census estimates.

Outside Florida, some US universities that run Confucius Institutes also said their programs are apolitical.

The CI at Western Kentucky University is not an academic unit, but a program supporting students of Chinese language, meaning it doesn't engage in political or religious activities, said director Weiping Pan.