When Defense Secretary Robert Gates used the word “threat” May 24 to describe China’s military modernization effort, it was a first for this administration and a clarion call to global strategists, observers say.

Although his combative predecessor, Donald Rumsfeld, was often accused of fanning concerns over Beijing’s buildup, it was Gates, the former CIA chief, who used the “T” word, saying the Pentagon’s 2007 report on Beijing’s military does not “exaggerate the threat.”

The statement came as U.S. and Chinese cabinet officers wrapped up unsuccessful talks about economic issues that cloud relations between two of the world’s biggest trading partners. China refused, for example, to link its devalued currency to the global free market or to earnestly pursue intellectual property infractions.

Beijing is pursuing similarly single-minded policies in the military sphere. In the past year, DoD’s report notes, China tested an anti-satellite weapon, accelerated development of land- and sea-based ballistic missiles, and stepped up work on nuclear missile submarines and mobile launchers.

Beijing also has probed U.S. defense computer networks for weaknesses, putting into action Chinese strategists’ contentions that destroying an enemy’s cyber-infrastructure is as important as physical attacks.

A decade ago, only a handful in official Washington regarded China as an emerging threat. Two who did were Andrew Marshall, head of the Defense Department’s Office of Net Assessment, and Michael Pillsbury, who wrote two books in the 1990s that argued that China was studying U.S. military vulnerabilities to draw its own modernization roadmap.

Over the years, both have been derided as alarmists, especially by those who argued that military confrontation was unimaginable for close trading partners. China is the leading purchaser of U.S. debt, while America is China’s biggest consumer-goods market. Besides, they said, Chinese defense spending was a fraction of the U.S. total.

Now, however, Marshall and Pillsbury appear prescient.

China is spending plenty — certainly more than it admits — to develop capabilities that go far beyond mere self-defense. It is militarizing commercial technologies — abetted by decades of close trade with European and other nations on “non-lethal” defense systems — and embracing asymmetric approaches to future war.

These efforts are fueling tensions that reverberate throughout the region. Japan is beefing up its security, alarmed by repeated incursions into its territorial waters and skies. That, in turn, alarms neighbors still stinging from Tokyo’s aggression in World War II.

As a nation known for detailing its strategic plans — for transport, for industry — China’s silence on its military future sets the stage for a destabilizing arms race. This military expansion is already increasingly cited by U.S. generals as reasons to revise their aircraft, ship and systems plans.

Does Beijing, as it claims, merely want a military commensurate to its rising global economic status? Or is it, as some fear, seeking the asymmetric teeth to secure economic resources or dictate global economic terms by force, if necessary?

Whatever the answer, this much is certain: An arms race is already brewing that could prove far more devastating than a spat over currency and pirated CDs.