Iran is pressured by lower oil prices. They accentuate the pain of existing sanctions and make it harder for it to meet budgetary targets, especially at prices now well below $100 per barrel.
There’s not much the West can do here, for now. Decreasing global oil dependence would help temper oil prices and is a smart, peaceful strategy against an oil-rich nuclear proliferator. But such comprehensive energy policy shifts are hard to bring about and will take years to accomplish, even with good leadership.