China's unwillingness to help with the nuclear build up

This is a good article about how the US is not putting enough pressure on China to pressure Korea to not test their weapons. I agree that the US is being too wishy washy, at least publicly, about putting serious pressure on China, as it appears to be the key to this puzzle.

http://www.nautilus.org/napsnet/sr/2005/0546ARPC.html