The OPEC nations have a vested interest in the continued health (such as it is) of the Euro; the Chinese want to see it devalued, but have to keep their own currency devalued in order to avoid losing sales in the US; the result is, the Chinese continue to use a chunk of their surplus trade dollars to purchase US gov’t debt, which keeps interest rates low (my ARM rate for the coming year just fell again, BTW; freakin’ property tax eval went down the past twelve months but the overall property taxes paid increased due to stupid local voters), and they do this in part to prop up the USD to avoid increased costs of their fuel imports, which would push up the cost of everything in their society, causing them to lose market share...
China will NEVER go along with sanctions on Iranian petroleum, count on it.