WASHINGTON (NYTIMES) - It sounds like something out of a science fiction movie: In April, China is said to have tested an invisibility cloak that would allow ordinary fighter jets to suddenly vanish from radar screens.
This advancement, which could prove to be a critical intelligence breakthrough, is one that US officials fear China may have gained in part from a Chinese researcher who roused suspicions while working on a similar technology at a Duke University laboratory in 2008.
The researcher, who was investigated by the FBI but was never charged with a crime, ultimately returned to China, became a billionaire and opened a thriving research institute that worked on some projects related to those he studied at Duke.
The Trump administration, concerned about China's growing technological prowess, is considering strict measures to block Chinese citizens from performing sensitive research at American universities and research institutes over fears they may be acquiring intellectual secrets, according to people familiar with the deliberations.
The White House is discussing whether to limit the access of Chinese citizens to the United States, including restricting certain types of visas available to them and greatly expanding rules pertaining to Chinese researchers who work on projects with military or intelligence value at US companies and universities.
The exact types of projects that would be subject to restrictions are unclear, but the measures could clamp down on collaboration in advanced materials, software and other technologies at the heart of Beijing's plan to dominate cutting-edge technologies like advanced microchips, artificial intelligence and electric cars, known as Made in China 2025.
The potential curbs are part of a broad set of measures the administration says are necessary to combat a growing national security threat from China, which it has accused of pressuring or coercing US companies into handing over valuable trade secrets.
But blocking Chinese citizens' access to American laboratories over fears of spying would be a significant escalation in an emerging cold war with the Chinese over which nation will claim technological dominance.
The details are still under discussion and it is not known how many people could be affected, but restrictions would probably fall most heavily on graduate students, postdoctoral researchers and employees of technology companies in the United States on temporary visas.
More than one million foreign students study in the United States each year, with roughly one-third coming from China.
The restrictions would cover Chinese nationals, but with two exceptions: those with green cards, which give them the right to permanent residency in the United States, and those who have been granted asylum because of persecution in their home country.
Also exempt would be former Chinese nationals who renounce their citizenship and become naturalized Americans.
An attempt to crack down on Chinese citizens could further chill relations between the two nations, whose closely integrated markets support the most prominent companies around the globe.
Technology companies like Apple, Qualcomm, IBM and General Electric have hitched their future growth to access to the Chinese market, which the Trump administration is now threatening to curtail.
This week, a delegation of administration officials, including Treasury Secretary Steven Mnuchin, will head to China for discussions to help avoid a brewing trade war. But additional curbs on Chinese citizens could make those tough discussions even harder.
President Donald Trump has threatened tariffs on roughly US$150 billion of Chinese goods in retaliation for unfair trade practices - a proposal that sparked tariff threats of China's own.
The administration is expected to detail new plans for restrictions on Chinese investment in the United States by the end of May. Congress is also considering giving the US broader authority to restrict Chinese investments.
These measures could prompt more damaging retaliation from China, which has already promised to place tariffs on at least US$50 billion of US products. They also appear to be fuelling anti-American sentiment within Chinese borders. China has tightened measures against possible spying, even posting public service announcements in subway trains warning citizens to watch foreigners for signs of espionage.
In the United States, research institutes look particularly vulnerable to espionage.
According to Defence Department statistics, nearly a quarter of all foreign efforts to obtain sensitive or classified information in 2014 were routed through academic institutions.
At a congressional hearing in April, Michelle Van Cleave, a former national counterintelligence executive, said the freedom and openness of the United States made the country a "spy's paradise".
Chinese and Russian agents both come to the US with "detailed shopping lists," she added.
Yet throwing up barriers to protect American technology could come at a high cost.
Restricting the free flow of people and information could disrupt innovation at US laboratories, a key destination for talented researchers from around the globe.
It could threaten the substantial profits that American universities earn from foreign students, who often pay full tuition.
And it could lead to discrimination. Some fear that the Trump administration's comprehensive challenge to China - always an easy political target in the United States - is cultivating a xenophobic, Cold War mentality in Washington that casts all Chinese people as enemies.
The Committee of 100, a group of prominent Chinese-Americans, has denounced government assertions that Chinese professors, scientists and students in the United States may be gathering intelligence for the Chinese government as "disturbing and prejudicial" and warned that it has overtones of anti-Japanese sentiment that was rampant during World War II.
"To target a whole group of people as being subject to greater suspicion, based purely on race and national origin, and in advance of any facts or evidence, goes against the fundamental American ideals of the presumption of innocence, due process and equal protection for all. It also fans the flames of hysteria," the group said in a statement.
Administration officials have been debating restricting visas offered to Chinese nationals for months as part of the broad package of measures targeting China economically. But the new plan under discussion by the White House would be a much more targeted measure, and one with potentially big consequences for American industry.
While the Obama administration also proposed barring foreign students from company-sponsored research at U.S. universities with national security implications, the Trump administration's measures could apply more broadly to private research facilities as well as new products and technologies.
The United States already restricts who can work on sensitive technology.
Researchers on projects deemed classified are carefully vetted and must obtain security clearances.
The next level down are research projects that are subject to so-called export controls - including many with potential military applications, such as computer programs and hardware that might be used to model nuclear explosions.
Universities and companies working on this material need to obtain a special license from the government to employ foreign researchers.
These products do not need to leave the United States to fall under export rules. All it takes to trigger export controls is for citizens from certain countries - including China, Russia and many former Soviet republics - to be involved in almost any way. That ranges from physical possession of the product to written descriptions and even verbal discussions of it.
The administration is considering broadening the range of goods and services traded with China that would be subject to these so-called deemed export rules.
If the proposal is approved by the Commerce Department, and ultimately by Trump, US companies and universities would be required to obtain special licenses for Chinese nationals who have any contact whatsoever with a much wider range of goods - making it harder for Chinese citizens to work on a range of scientific research and product development programmes.
Fuelling the push are instances like the one involving Ruopeng Liu, a Chinese citizen and a promising student at Duke who was helping to develop a cloak that shields objects from a broad spectrum of wave frequencies.
The professor leading the Pentagon-funded lab, David R. Smith, became suspicious of Liu, who seemed intent on collaborating with old colleagues in China, and even invited them to tour the lab and photograph Duke's equipment.
It became clear to Smith that Liu was trying to share the cutting-edge technology he was studying in the United States with colleagues in China. The institute he founded on his return to China eventually received millions of dollars of investment, registered thousands of patents and even played host to President Xi Jinping of China.
Liu did not respond to interview requests, but in past interviews, he has maintained that he did nothing wrong, beyond taking advantage of an open and collaborative university atmosphere.
Like many projects in the United States, most of Smith's work at Duke was early-stage research that was not classified or categorized as a deemed export.
Daniel Golden, who tells Liu's story in his book, "Spy Schools", said Liu exploited a gray area that allows a large amount of sensitive, taxpayer-funded technology to flow to foreign governments.
"Globalization has transformed American universities into a front line for espionage," Golden said.
Yet the academic community is likely to push back on the administration's efforts over concerns that tighter controls on Chinese nationals could hurt American universities' ability to collaborate on cutting-edge research and wind up benefiting China even more.
Many students at graduate programs in the United States in computer science, physics, chemistry and other sciences are from China.
If the United States makes it harder for aerospace manufacturers, defence contractors and others to employ Chinese nationals, more of these recently trained Chinese graduate students may return to China, taking their skills with them.
Stephen A. Orlins, the president of the National Committee on US-China Relations, said that restricting Chinese researchers would be "tragic" for American universities.
"It's important that we don't let the security fears overwhelm what has made America great," he said.
Even Smith said he did not support tougher restrictions on Chinese researchers. Instead, he said, universities should better educate researchers about existing rules and what to do in case of intellectual property theft.
"With reasonable safeguards I think we can manage it," he said.
"If we were to overreact, I think it could be very damaging to our universities."