While we are trying to convince the Chinese to join us in sanctions on Iran (or at least not to veto them), China is on the verge of announcing sanctions against American companies for selling arms to Taiwan (a/k/a the Republic of China, or ROC).
The sanctions at this point are only threatened, not put in place, but, short of deciding that that measure may be an overreaction--which doesn't seem likely to me--I don't see what would stop them. The Chinese government's point of view is that selling arms to Taiwan is an intolerable intrusion in their domestic affairs, while ours is that we are obligated by policy and treaty to provide military necessities for the defense of Taiwan.
The American arms companies involved probably just have to look at the enmity of China (a/k/a the Peoples' Republic of China, or PRC) as an unavoidable negative effect of being a good customer of the US military (while the sales to Taiwan are an unavoidable fringe benefit).
To me, China's making a big campaign against the arms sales is a mistake--when was the last time anyone outside the region noticed the existence of Taiwan?--though China considers it a principled objection to an intentional policy of disrespect to their claimed sovereignty over the "renegade province". A more suspicious person might look at the sales as a potential direct harm to Chinese soldiers if the day ever came when they decided to take Taiwan back by force (as the PRC threatens to do, if Taiwan ever dared declare their independence from the mainland).
The unsettled status of Taiwan would probably be the last thing the US government needs to bring up in these trying times, when China's cooperation is needed on so many matters of international diplomacy and economics. With the return to unchallenged political control of the KuoMinTang (the KMT, the party of Chiang Kai-Shek), things are back to "normal" ambiguity, in which both the ROC and the PRC have a position that Taiwan is part of China--there's just a technical dispute about who's in charge.
The only major declared enemy of this permanent temporary anomaly, former ROC President Chen Shui-bian, is now in prison somewhere near Taipei, serving a sentence of life imprisonment for corruption crimes. His prosecution was nothing but murky; he admitted some violations on campaign financing, and his wife and son admitted more, but the whole thing also smacks strongly of political motivation and placation of the mainland power.
During his heyday, in the early days of his 2000-2008 term in office (like George W. Bush, he somehow managed re-election in 2004 under unusual circumstances and deep internal dissatisfaction), "A-bian" dared to speak truth to power and suggest a couple of heresies: 1) the people in Taiwan don't want unification with China while the PRC continued to violate the civil liberties of its citizens, thank you very much; and 2) federation is the long-term solution for Greater China which would both permit the Han Chinese their pre-eminent political role in Chinese civilization, yet allow the multiple nationalities (Taiwanese, Uighur, Tibetan, the westernized Hong Kong Chinese, and, believe me, many others) in the Chinese-speaking world to exercise their own rights of free expression. Is it for this that the disgraced head of the unofficial party of Taiwanese independence (the DPP) must pay?
Probably the imprecation does some injustice to the rough-and-tumble democracy, and the semi-independent judiciary, of the ROC. Taiwan's government suggests to me many of the characteristics of the Italian government (but with superior economic management): chaotic, corrupt, untrustworthy, but unmistakably, unshakably, their own.