Drezner counters Roger Cohen:
I seriously doubt that the United States can offer anything to get Tehran to halt its nuclear program. This leads to one of two possible decisions: pre-emptive action to delay the program, or accepting the inevitable.
Contra Cohen, the most pragmatic thing for the United States to do is to expect nothing fruitful to come from negotiations with Iran -- and to (nonviolently) prepare for the contingency of a nuclear Iran.
I see no realistic way of avoiding it.