For the second time, since 1999, that a Chinese general has said, openly, that China would use nuclear weapons against the United States if China found itself fighting American forces in some future war. The most likely source of conflict would be American intervention during a Chinese attempt to invade Taiwan. The major general who made the comment was an instructor at China's senior defense institution (National Defence University). This is the kind of place where China's brightest military minds develop strategies for future wars. The decision to use  nukes is an admission that China believes its conventional forces would not be able to deal with intervention by American air force and navy units. The only catch with this threat is that, at the moment, China doesn't really have any reliable way to deliver a nuclear weapon to the United States. So the threat bespeaks desperation as much as an admission of military inferiority. As happened in 1999, the government later downplayed, but did not deny, the nuclear weapons comment.