Perry is among thousands of Americans who meet regularly with their Chinese counterparts in exchanges on scientific, military and technological subjects that have drawn warm praise from both sides.
But now, as charges of lax security reverberate through the nation's military-scientific community in the wake of the espionage probe, academics and experts are bracing for a new climate of suspicion that could freeze this growing cooperation.
"I agree that it could lead to a new round of McCarthyism, or something very much like it," said Ronald Montaperto, a senior research professor at National Defense University and a China specialist. "I have never seen a response like this before," he said, referring to the intense Washington reaction to the spying charges.
The scrutiny is especially intense at the three U.S. nuclear weapons research facilities, the Los Alamos, Lawrence Livermore and Sandia laboratories. Los Alamos, where the alleged theft occurred, welcomes hundreds of Chinese scientists in a U.S.-China, lab-to-lab program begun in 1995, aimed at fostering long-lasting professional relationships.
Early alarms
A decade ago, when the number of foreign visitors at the labs was only a fraction of what it is today, the General Accounting Office began sounding the alarm about loose controls. But the Energy Department only recently clamped down on security.
Ever since the Manhattan Project -- code name for the development of the atomic bomb in World War II -- the nation's nuclear weapons laboratories have been torn between the desire for intellectual freedom and the sharing of ideas, and the constraints of national security.
"To get your work done most effectively, you want anyone who can understand what you're doing, anyone who can critique your approach or theory, to weigh in," said Michael May, a prominent physicist and retired director of Lawrence Livermore in California. "But conversely, the more people that know, the more chance there is for a leak."
Washington officials imagine the labs as military fortresses securing some of the nation's most sensitive secrets. But the scientists see their sprawling laboratories as academic campuses where they conduct cutting-edge scientific research, some of which happens to relate to nuclear weapons.
And scientists do not believe vital scientific advances can be kept secret. A seminal report to the federal Defense Science Board in 1970 by a task force of eminent scientists concluded that important classified information is unlikely to remain secure for more than five years, and is more likely to become known within 12 months of discovery.
Controls more difficult
As the science of nuclear weaponry becomes increasingly complex, the laboratories' esoteric research is becoming increasingly difficult to classify as defense- or non-defense-related, making security controls that much more difficult.
For instance, Hugh DeWitt, a Livermore physicist, is conducting joint research projects with Chinese scientists on the effect of extremely high temperatures and pressures on different materials. The work could reveal more about the inner workings of stars, but it could also shed light on the inner workings of hydrogen bombs.
"This is problematic from the viewpoint of Washington, D.C., but not from the laboratory," DeWitt said, adding that "it is very appropriate for the labs to have good contacts with outside scientists."
Security officials in Washington occasionally appear baffled by these scientists. "The culture of science and culture of security are fundamentally at odds," said Steven Aftergood, director of the project on government secrecy at the Federation of American Scientists. "Scientists want to publish, and they want to discuss their findings, because that's how they learn new things and that's how they discover mistakes."
Scientific cooperation is one of the areas most prone to security leaks but is just one of many areas in which Americans and Chinese share their knowledge and ideas.
"The extent, purpose and variety are multitudinous," said Jan Berris, vice president of the National Committee on U.S.-China Relations, which sponsored the recent trip by Perry and a group of prominent American national security experts.
Ties between medical researchers have led to important exchanges on cancer, she said.
In both countries, there are often close ties between the top scientists and national-security establishments. Perry, a mathematician, is one example. As defense secretary in President Clinton's first term, he stepped up military exchanges with the Chinese on the theory that the better they understood the United States and its capability, the less likely they were to blunder into war.
Some of the most rarefied exchanges occur at the Stanford Linear Accelerator Center in Palo Alto, Calif.
"Being there, you are with people at the cutting edge of theoretical physics, some of whom have been involved in security programs," says Spurgeon Keeny, president of the Washington-based Arms Control Association.
A senior Stanford scientist, Sidney Drell, serves on the president's Foreign Intelligence Advisory Board and has also given high-technology advice to the U.S. military. Keeny and other weapons and arms-control experts meet regularly with their Chinese counterparts through the National Academy of Sciences.
In these exchanges the overlap between scientific research and military use is well-known. The American participants are usually experienced enough not to spill whatever secrets they know.
But in a world of global-positioning satellites and lasers, scientific and military technologies are often fungible, producing numerous dual uses and gray areas.
U.S. high-technology firms are under pressure to transfer commercial technology to the Chinese as a condition of conducting business, according to a recent Commerce Department report.
A crash of a satellite launcher ignited the furor over Chinese espionage. In trying to help the Chinese correct the fault in their rocket guidance system, a U.S. firm gave out information valuable in missile development.
"We ought to stay engaged with China -- and Russia, too -- but you've got to make sure your pocket isn't picked," said former CIA Director James Woolsey.