The US revoked the visas of more than a thousand Chinese students and researchers for national security reasons, in the latest escalation of tensions between the world’s two biggest economies.

The visas were revoked under a measure intended to limit China’s ability to use graduate students and researchers to steal US “technologies, intellectual property and information to develop advanced military capabilities,” a spokesman for the US embassy said in an emailed statement Thursday.

The people who had their visas revoked “represent a small subset” of students and scholars going to the US, according to the statement, which said that the US continues to welcome “legitimate” students and researchers.

The news was earlier reported by Reuters.

The visas were canceled under a May presidential proclamation which targets Chinese citizens with ties to the People’s Liberation Army, the statement said. No information was provided about the individuals whose visas were canceled.

People on Chinese social media speculated that the students were likely connected with or graduates of seven Chinese universities and their affiliated schools which are connected with national defense.

The cancellations are likely to add to the uncertainty Chinese students face about studying or working in America. The Trump administration earlier vowed to deport all foreign national students if they didn’t take in-person classes during the pandemic, only to withdraw that rule days later, leaving students perplexed and worried about their legal status in the States.