Sorry A4O, but you are missing some vital information on the US debt/ china bond front:
China has close to 2 trillion in US bonds and continues to buy them as a mechanism for helping to keep down the value of the RMB - if it doesn't continue this cycle then Chinese exports become too expansive and it stalls Chinese economic growth. So stopping the debt buying cycle would crush China's move in the short to medium term to a consumer economy and selling any bonds on a significant level would have an ever bigger effect. A flood to the market would raise the yield as the value drops so china would see a huge depreciation in its investment should it choose to go down that path. Given the problems that governments have raising capital, the value drop would have to be substantial, in line with the required increase in yields to tempt the willing investor.
With such a large hand in the us bond market, china has a vested interest in maintaining the health of the market - if you remember, china even waded into the debt ceiling debate a while back and implored the US gov't to resolve the issue to help protect chinese investments. Taking into account that the US bond market is the only market large enough to deal with china's excess surpluses (though they are falling) without major disruption it really is a case of china needing the US as a close economic ally, as much as the US needs china.
China has always been wary and distrustful of Russia - with good reason - so I think the apparent coziness is more to do with keeping your friends close and your enemies closer.
China would drop russia like a hot potato given the need.
