China's real strategic problem with respect to the proliferation of nuclear weapons is very simple - anything the North Koreans can do the Taiwanese can do better. And may well be doing as we speak. This was definitely not a step in the right direction for Chinese regional geopolitics.
It would really be interesting should the Taiwanese decide to purchase the necessary materials from the North Koreans. Don't think the Chinese haven't thought of it.
A long time ago in a World where four nations stood alone, outside the United Nations, surviving on the "good will" election cycle of American electoral politics... Taiwan, South Africa, South Korea and Israel banded together to explore nuclear weapons. Much spectulation about nuke explosions off the S. African coast sever times in the 78-80 period, possibly ending in a pre-Lybian first of WMD transfer, e.g., the transfer of S. Africa to a less stable regime for military purposes (no longer a Western oriented Nations). Today, Israel is accused, or rather suspected, of having acquired the bomb - and one wonders how or where they tested it. More than a few governments around the world know how to connect the dots of the four countries. It took years for South Korea to join the UN in a prelude to their '88 Olympics - a major US coup on the International stage. Taiwan awaits either the fait of South Africa or continued world presence like Israel.
So does anyone out their think that North Korea would not have attacked the South, or that the Arabs would not have attacked Israel, or better yet why was China deterred by puny Taiwan.... I rather beleive the scientific exchanges in the 70-80's put these countries into a very quiet, technolgical and secure, military viable sustaining regimes.
A Nuclear Japan and Taiwan ends China's hopes of becoming THE Regional Power in Asia, and they know it...
The U.S. can be easily countered, simply by playing to the Surrender element/Democrats, as they have done in the past, but a Nuclear Japan/Taiwan Club will not be so easy to overcome...