From a press release two weeks ago, the Chinese have made it clear (if it wasn't already), that targeted sanctions will not receive Beijing's support. Now you're probably saying "But what about the progress made at the UN?" Well, sanctions are being developed, but they will fall far short of the targeted ones on petroleum exports that Washington wants. The only thing a UN Security Council resolution will do at this point will green light the tough sanctions Obama really wants for passage by Congress. And since the U.S. already has imposed several sanctions on the nuclear wannabe, it's doubtful that they'll work. I fully expect that Iran will become a nuclear state within my lifetime.
I won't claim to be an expert on Iranian affairs, but the nuclear issue seems to be the only thing Western countries are desperate to talk to Iran about. Moreover, rights to nuclear technology present a rally around-the-flag topic that Tehran can use to remain in power. Seems to me that it might be worthwhile to try to buy off Iran as opposed to whacking it with sanctions. Some people may resent rewarding Iran for its negative behavior, but sanctioning Iran is a lot like withholding a child's allowance until they behave. Sometimes it takes corporal punishment. However, no country (with the exception of Israel) is advocating a military strike.
I'll close off with a general criticism of sanctions. In order for sanctions to be effective, the targeted country needs to know what it should do to have them terminated. If one looks at UN Security Council resolution 1737, it says that Iran must halt all R&D on nuclear technology and enrichment. Considering that Iran needs alternative sources for energy production because of the sanctions currently placed on it, this is asking A LOT. No wonder Iran is pursuing what is in its interests.