The US has insisted it is committed to welcoming Chinese nationals for “legitimate” studies but acknowledged increased visa scrutiny after Beijing warned its students of risks.

Amid an escalating trade war between the world’s two largest economies, China’s education ministry pointed to an uptick in visa denials and delays. It told students applying to US universities to brace themselves and “strengthen risk assessment”.

A decrease in Chinese students could be costly to the US. China is by far the biggest source of international students on US campuses, with 360,000 attending last year. Many pay costly full tuition.

The State Department said it had increased scrutiny after identifying a rising number of cases in which foreign intelligence services co-opt students during their time in the US.

“At the same time, we’re committed to providing the highest quality service to legitimate travelers – who constitute the overwhelming majority of our visa applicants – so they can receive swift, thorough and clear decisions regarding their visa applications,” a State Department spokeswoman said.

“We welcome Chinese students and scholars to the US to conduct legitimate academic activities,” she said, saying that most applicants receive full five-year visas.

Xu Yongji, deputy head of a department overseeing foreign academic exchanges at China’s education ministry, said that visa denials have “damaged the dignity” of Chinese students and cast a “cold spell” over research collaborations and academic exchanges.

From January to March, more than 1,350 Chinese students had applied for US student visas, but 182 were “unable to make the trip as planned” due to visa issues, accounting for 13.5 per cent of all applicants, Xu told state broadcaster CCTV.

Citing data from the China Scholarship Council, Xu said this was a marked increase from just over three per cent of applicants who experienced visa issues last year.

China’s foreign ministry spokesman Geng Shuang said the US had been setting “unnecessary obstacles” to people-to-people exchanges between the two countries.

Major economic impact

Chinese students contributed $14 billion to the US economy in 2017, according to a trade group.

India is the second largest source of students but the gap is significant, with fewer than 200,000 Indians studying in the US.

US complaints about technology and intellectual property theft by China have been a major bone of contention in the trade war between the two countries.

FBI director Christopher Wray said in April that Beijing had used Chinese graduate students and researchers, among others, in its economic espionage efforts in the US.

“China has pioneered a societal approach to stealing innovation in any way it can from a wide array of businesses, universities and organisations,” Wray said.

“They’re doing it through Chinese intelligence services, through state-owned enterprises, through ostensibly private companies, through graduate students and researchers, through a variety of actors all working on behalf of China.”

Last month, Republicans in the US Congress introduced legislation aimed at barring Chinese military scientists from obtaining visas to study or work in the US.

Obtaining a visa to travel to China can be an onerous process for tourists and especially for journalists, and they can be denied with little explanation.

But as Chinese universities continue to rise in global rankings they have become attractive destinations for foreign students.

There were over 492,000 foreign students from 196 countries studying in China last year, though the number of Americans fell from almost 24,000 in 2016 to around 21,000 last year, according to data from the education ministry.