If they're true, the spy charges against China made this week by a congressional committee would represent perhaps the most serious breach of US security since the Soviet Union stole basic nuclear secrets at the dawn of the Atomic Age.
Whether they will lead to a new cold war, with Beijing playing the role of Moscow, is another matter.
The US-China relationship has long been characterized by wide swings in emotion, at least on the part of the Americans. From the "who lost China?" debate following the 1949 Communist takeover, to the surge in interest that followed President Nixon's resumption of relations, US attitudes toward the Middle Kingdom have varied between demonization and romanticism.
In recent years, ties have tended to snap back to a middle course, like a spinning top that rights itself after being tilted. The reason: US and Chinese interests overlap in a way that US-Soviet interests didn't.
"We don't have a strategic partnership or alliance with China. But we have to have constructive relations, there needs to be a continuing dialogue," says Nancy Bernkopf Tucker, a history professor at Georgetown University.
That said, it does look as if the spy charges could exacerbate tensions - which peaked when a US error led to NATO missiles hitting China's Embassy in Belgrade May 7 - in what is likely to be a difficult 18 months for the US and China.
There are a series of events coming up that could provide further irritants, from an inevitable summer congressional debate over China's trade status, to a US presidential election in which policy toward China could well become a major issue, as it did in 1992 when candidate Clinton charged incumbent George Bush with coddling Chinese dictators.
"My sense is that looking back in time we will see 1999 as ... one of those markers in Chinese-American relations that was a time of great turmoil and crisis," says Professor Tucker.
The 900-page report produced by a select House committee headed by Rep. Christopher Cox (R) of California lays out troubling circumstantial evidence that China has been engaged in a 20-year effort to steal American's crown jewel nuclear secrets.
The report alleges, for instance, that China has obtained secret data on every warhead now in the US arsenal, and at least one, the neutron bomb, that America decided not to build. If true, the charges would "quite definitely" be the worst since Ethel and Julius Rosenberg were convicted in the early 1950s of passing top-secret information about early atom bombs to a Soviet agent, says June Teufel Dreyer, a political scientist at the University of Miami, Coral Gables. "This was systematic, and went on for years," she says.
Recent revelations have indicated that Soviet penetration of the US atomic program was much more thorough than previously thought, however. Newly declassified US electronic intercepts, plus the opening of old Soviet archives, have dropped such hints as the allegation that the first Soviet atomic bomb, detonated in 1949, was an exact copy of a US model.
New research supports the assertion of a Stalin-era KGB official that a Sante Fe, N.M., drugstore served as a safe house for Soviet spies after World War II.
Such theft helped fuel a nuclear-arms race, which in turn contributed to the long standoff of the cold war. But espionage alone was not at the root of the US-Soviet competition. The massively different economic world views of capitalism and communism ensured conflict on a wide range of fronts.
CHINA remains nominally Communist, but the controlled capitalism of its economic system has long given it a shared interest with the US in economic development. From its desire to enter the World Trade Organization to its need for American products and export markets, China has at least some incentives to deal positively with the world's only superpower.
The US, meanwhile, seems to swing between a view of China as an economic ally, as if it were a Japan that just happens to have nuclear weapons, or as a military adversary, a North Korea that's functional.
The need now, say many experts, is for the US to separate the various strands of its relationship - military, economic, and human rights - and weigh the true importance of each.
"There is room to criticize China and our own security policies while engaging China," says Patrick Cronin, a US Institute of Peace expert who was a high Pentagon official for most of the Clinton years. "We need to walk and chew gum at the same time."