The noose is tightening around Iran. (Fitting, isn't it?) China is dragging its feet, but the United States has considerable leverage to exercise against China -- loss of "most favored nation" status; curtailing wheat and grain exports to China upon which China depends to feed its enormous population (or making them prohibitively expensive); loss of outsourced manufacturing jobs -- there's lots the United States can do to bring China to heel. The last thing on earth that China wants is to be cast in the same pariah role as Iran. No amount of oil (which is readily available elsewhere, anyway) is worth it, and China knows this.
In any event, Iran is reduced to bartering with those few nations still willing to do business with Iran.
The end of the Islamic Republic is nigh.