The United States is targeting only about one percent of the 400,000 Chinese students in the United States over China’s bid to gather U.S. technology and other information, a top White House said official said on Wednesday.

Matt Pottinger, the deputy White House national security adviser who has been a leading figure in the development of President Donald Trump’s China policy, said the vast majority of Chinese students were welcome.

“It’s a surgical approach,” Pottinger said in a online event hosted by the Ronald Reagan Institute, referring to the administration’s policy of denying student visas to Chinese nationals it considers a security risk.

“President Trump has taken action to target roughly one percent of that massive number, to target military-affiliated Chinese researchers who are in some cases here under false pretenses or even false identities,” he said.

Other cases involve individuals who have come to the United States to gain access to “technologies that would be useful to Chinese military advancement or to the repression of their own people,” he added.

Pottinger said the overwhelming majority of Chinese students were “people that we’re glad to have here, and many will stay here and start great businesses.”

The U.S. action against Chinese students has come at a time when China-U.S. relations have sunk to the lowest point in decades in the run-up to Trump’s Nov. 3 re-election bid. The world’s two biggest economies have clashed over issues ranging from trade and human rights to Hong Kong and the coronavirus.

The U.S. State Department said this month the United States had revoked visas of more than 1,000 Chinese students and researchers deemed security risks. China called this a violation of human rights.

Washington said the action followed a May 29 proclamation by Trump in response to China’s curbs on democracy in Hong Kong.

The large number of Chinese students studying in the United States bring significant revenue to U.S. universities, although the COVID-19 pandemic severely disrupted returns to campus this fall.