In interviews over the past two days, American officials with access to the intelligence on the test said the United States kept mum about it in hopes that China would come forth with an explanation.

It was more than a week before the intelligence leaked out: a Chinese missile had been launched and an aging weather satellite in its path, more than 800 km above earth, had been reduced to rubble. But protests filed by the United States, Japan, Canada and Australia, among others, were met with silence—and quizzical looks from officials in The Chinese Foreign Ministry, who seemed to be caught unaware.

In an interview late Friday, Stephen J Hadley, President Bush’s national security adviser, raised the possibility that China’s leaders might not have fully known what their military was doing.

“The question on something like this is, at what level in the Chinese government are people witting, and have they approved?” Hadley asked. He suggested that the diplomatic protests were intended, in part, to force Hu to give some clue about China’s intentions.

The threat to United States interests is clear: the test demonstrated that China could destroy American spy satellites in low-earth orbit (the very satellites that picked up the destruction of the Chinese weather satellite).

As a result, officials said, the test is likely to prompt an urgent new effort inside the Bush administration to find ways to counter China’s antisatellite technology.

American officials noted that the US and Russia had not conducted such tests for two decades, and that the international norm had changed, in part because so many private satellites had been launched by many nations. “The Chinese seem out of step on this one, and we don’t know why,” one official said.

But the more immediate mystery about the destruction of the satellite revolves around China’s prolonged silence— and what it says about the commitments President Hu and President Bush have made concerning increasing their communication, and diminishing the secrecy around China’s military buildup.

The timing is significant. Chinese officials have hinted in recent months that they are prepared to grant an American request to establish a military-to-military hot line that may be used to enhance communication. But China has moved slowly to establish the link.

-DAVID E SANGER & JOSEPH KAHN