The United States and its allies vowed this week to do more to counter Chinese theft of technology, warning at an unusual gathering of intelligence leaders that Beijing’s espionage is increasingly trained not on the hulking federal buildings of Washington but the shiny office complexes of Silicon Valley.

The intelligence chiefs sought to engage private industry in combating what one official called an “unprecedented threat” on Tuesday as they discussed how to better protect new technologies and help Western countries keep their edge over China.

The choice of meeting venue — Stanford University, in Silicon Valley — was strategic. While Washington is often considered the key espionage battleground in the United States, F.B.I. officials estimate that more than half of Chinese espionage focused on stealing American technology takes place in the Bay Area.

It was the first time the heads of the F.B.I. and Britain’s MI5 and their counterparts from Australia, Canada and New Zealand had gathered for a public discussion of intelligence threats. It was, in effect, a summit of the spy hunters, the counterintelligence agencies whose job it is to detect and stop efforts by China to steal allied secrets.

“That unprecedented meeting is because we are dealing with another unprecedented threat,” said Christopher A. Wray, the F.B.I. director. “There is no greater threat to innovation than the Chinese government.”

The warnings come as the United States and China engage in an intense, and expanding, spy-versus-spy contest, and as U.S. officials say that China’s espionage efforts have reached across every facet of national security, diplomacy and advanced commercial technology in the United States and partner nations.

The intelligence chiefs said they were making the case to private industry that the security interests of the West were aligned with their business interests. No one profits if China steals intellectual property, they argued.

The spy chiefs said China is intensely interested in Western artificial intelligence, a technology that will allow countries to improve their intelligence collection and analysis and is set to be a driver of economic gains for years.

Just before the spy chiefs met on Tuesday, the Biden administration announced that it was limiting the sale of advanced semiconductors to China, a restriction that could curb China’s development of artificial intelligence.

At a news conference on Tuesday evening, Mr. Wray said China was stealing American technological know-how and then turning around and using the stolen knowledge to steal more.

“They are using A.I. to improve their already massive hacking operations, in effect using our own technology against us,” Mr. Wray said.

Ken McCallum, the director general of MI5, said that the number of investigations into Chinese espionage had risen substantially in Britain since 2018, and that China had increased the number of approaches it has made to potential informants there. The technologies China is trying to steal have potential to transform both economics and security, and China is undertaking an ambitious effort of large scale, he said.

“If you are anywhere near the cutting edge of tech, you may not be interested in geopolitics, but geopolitics is interested in you,” Mr. McCallum said.

The intelligence chiefs said China was using hacking, pressure on Chinese students, informants in Western companies and joint ventures with Western firms to try to steal critical technology.

David Vigneault, the director of the Canadian Security Intelligence Service, said Western companies needed to understand that China had “changed the rules of the game.” He said laws in China compelled its nationals anywhere in the world to provide information to Beijing’s intelligence services.

“It means they have a way to coerce people here in our countries to essentially tell them, to give them the secrets,” Mr. Vigneault said.

U.S. national security officials have said that preventing Beijing from imposing its rules on people overseas is a top priority. The United States is working to shut down illegal overseas police stations that the Justice Department says are used to monitor and intimidate dissidents.

Mike Burgess, the director general of the Australian Security Intelligence Organization, said China was exploiting the openness of the West, and the desire of Western universities to collaborate.

“All nations spy, all nations seek secrets and all nations seek strategic advantage, but the behavior we are talking about here goes well beyond traditional espionage,” he said.