By Jonathan Marcus
BBC Diplomatic Correspondent
Quite apart from chronicling the build-up and modernisation of Beijing's armed forces, the tone of the Pentagon's annual report to Congress on China's military power is always closely studied for a wider sense of the way in which China is being seen in Washington.
Washington is keeping a close watch on China's rise
This year - at least from the Pentagon's perspective - there seems to be something of a toughening of the mood.
China, it says, is at a strategic crossroads, and choices made by Beijing will have significant implications not just for Sino-US relations, but also for the Asia-Pacific region - indeed for the whole world.
China's rise - its extraordinary economic development, its trade-led diplomacy and its growing appetite to play a role on the international stage - look set to be one of the defining themes of global development in the decades ahead.
China's military build-up is only one part of this process.
For now, it is viewed by the Pentagon as being very much related to China's long-standing dispute with Taiwan.
But in the longer term, modern military forces could become a more significant element in China's regional role.
What is worrying many China analysts is that the Bush administration's approach to the country seems to be a piece-meal one, lacking over-arching principles and thus capable of being thrown off course by minor squalls.
A Chinese bid for a US oil company with significant assets in Asia has alarmed US conservatives and prompted calls for protectionist legislation.
Of course the fact is that China, as one of America's most important creditors, is already funding a significant element of the US debt.
Whatever the day-to-day tensions, Washington and Beijing are inextricably bound up in each other's fate.