NORTH CAROLINA (NYTIMES) - Duke University has apologised after a professor cautioned international students against speaking Chinese on campus and urged them to speak English instead.

Professor Megan Neely issued the caution in an e-mail last Friday (Jan 25).

Prof Neely has since asked to step down from her role as director of graduate studies in the medical school's biostatistics master's programme, Duke medical school dean Mary E. Klotman said in a letter to students last Saturday.

Prof Neely did not respond to e-mail requests for comment on Sunday. A university spokesman confirmed that she remained on the faculty as an assistant professor of biostatistics and bioinformatics.

Prof Neely said in the e-mail that two faculty members had come to her office complaining about students speaking Chinese "very loudly" in the student lounge and study areas.

The faculty members wanted to identify the students and write down their names, she said, in case the students sought to work with them in the future.

"They were disappointed that these students were not taking the opportunity to improve their English and were being so impolite as to have a conversation that not everyone on the floor could understand," she wrote in the e-mail.

"To international students, PLEASE PLEASE PLEASE keep these unintended consequences in mind when you choose to speak Chinese in the building."

She added that she had the utmost respect for international students. "That being said," she wrote, "I encourage you to commit to using English 100% of the time" in a professional setting.

The university confirmed the authenticity of the e-mail, which was widely shared on social media.

In February 2018, Prof Neely sent a similar e-mail, which a university spokesman also verified. In that e-mail, she acknowledged that living and studying in a foreign country was a "tremendous undertaking", but relayed that faculty members were concerned about students speaking foreign languages in the department's break rooms.

"Speaking in your native language in the department may give faculty the impression that you are not trying to improve your English skills and that you are not taking this opportunity seriously," she wrote.

"As a result, they may be more hesitant to hire or work with international students because communication is such an important part of what we do."

In her letter, Professor Klotman, the dean, apologised to students and said she had asked the university's Office for Institutional Equity to conduct a "thorough review".

"I understand that many of you felt hurt and angered by this message," she added.

"To be clear - there is absolutely no restriction or limitation on the language you use to converse and communicate with each other. Your career opportunities and recommendations will not in any way be influenced by the language you use outside the classroom."

Prof Neely's e-mails drew criticism and reflected broader tensions about the way Asian and Asian-American students are viewed in academia.

In 2011, a University of California, Los Angeles student ranted on YouTube about the "hordes of Asian people" at the university and complained about their cellphone use at the library.

International Chinese students also face unique challenges, including suspicions that they may be spying for their home country.

Mr Ken Lee, chief executive of OCA-Asian Pacific American Advocates, said he was disappointed by what he described as an "ignorance and hateful bias against students".

"Forcing students to repress their heritage language further perpetuates a wrongful culture of fear towards Asian and Asian-American students," he said in a statement on Sunday.

About 35 of the 54 students in Duke's master of biostatistics programme are Chinese, according to the university. About 10 of the 50 faculty members in that programme are Chinese, the university said.

More than one million foreign students study in the United States each year, with roughly one-third coming from China. But universities have seen a decline in international student enrolment.

International enrolment began to flatten in 2016, partly because of changing conditions abroad, but also, college administrators said, because US President Donald Trump's rhetoric and more restrictive views on immigration have made the country less attractive to international students.

In a letter dated last Saturday, a group of international students at Duke petitioned the university to investigate what happened leading up to Prof Neely's e-mail, including the actions of the other faculty members.

The group said in a statement on Sunday that the e-mails showed "an appalling lack of knowledge and understanding about the Chinese culture and community".

"We wrote the petition to combat the normalisation of xenophobia and discrimination against Chinese students at Duke," the students said.

Ms Yung-Hwa Anna Chow, who advises students in Washington State University's college of arts and sciences, said international students must have English proficiency to study in the US. While students may need to speak English in classrooms and research labs, they should be able to choose which language to speak in social settings, she said.

"To attack these students and say they have to speak English because it's good for them and that they need to practise more, it speaks to these professors' privilege and entitlement," she added.

Ms Chow, who was raised in Taiwan and began learning English at 12 when she moved to the US, said speaking a native language allows people to connect with one another, establish a feeling of home and combat homesickness.

"That's a really important piece for these students," she said. "If you were travelling to China and you didn't speak Chinese, would you want to be speaking Chinese all the time or would you feel more comfortable speaking English with your friends?"