The widespread and sometimes violent protests that have erupted in China since the bombing of the Chinese embassy in Belgrade present the country's leadership with a dilemma.
They are the biggest demonstrations directed against any foreign country in China since Beijing began opening its doors to the outside world two decades ago.
They also involve the biggest participation by students in public protests since the Tiananmen Square unrest of 1989.
Speaking to the American network NBC, the US Ambassador to China James Sasser said he thought the protests were exceeding the government's expectations.
He said there was a danger that they could, as he put it, go out of control.
Anti-American feeling
To a leadership which often accuses America of trying to subvert the communist system, it must be satisfying to see such an outpouring of anger directed at the United States.
These have been by far the biggest anti-American demonstrations in China since the Cultural Revolution of the 1960s and 70s.
Ten years ago in Tiananmen Square, students enraged the government by erecting a statue similar to New York's Statue of Liberty.
Now they are cursing Americans in much the same language that the government itself is using.
The Chinese leadership must also be concerned, however, about the danger of nationalist sentiment being exploited by political dissidents.
The leadership has frequently stressed the paramount importance of maintaining social stability this year because of the risk that sensitive anniversaries.
These have included that of the 1989 unrest as well that of the founding of communist China 50 years ago.
The dates could be used by dissidents to air their grievances.
At a time of widespread public discontent over unemployment, corruption and an economic slowdown, the leadership fears that any protests could trigger serious instability.
It is also likely to be worried that a sustained wave of anti-Western unrest could scare away foreign investors.
Leadership concerned
However, attempting to curb the angry gatherings outside American and British diplomatic missions is fraught with potential risks for the government.
If the authorities were to crack down in a way deemed too heavy-handed by participants, there is a danger that student and indeed general public anger could be redirected towards the government.
Sunday's televised speech by the vice president Hu Jintao appeared to reflect the leadership's concerns.
While paying tribute to what he called the keen patriotism of participants, he warned against people making use of the opportunity to disrupt social order.
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