Dan Drezner answers questions about Iran and sanctions. He responds to the idea of imposing more sanctions to force regime change:

Repeat after me: sanctions, on their own, will not lead to a regime change in Iran. Over the past five years this regime has made it pretty clear what it is willing to do to stay in power. That trumps any ratcheting up of the sanctions. Economic coercion imposes some serious economic costs on the regime, which is why they’re willing to talk about a nuclear deal. But that’s a tangible negotiation. Regime change is more existential threat, and if that’s the goal of the sanctions, then the sanctions will fail and fail spectacularly.

If there’s one thing that we know that sanctions can’t do, it is forcing regime change. Sanctions weaken domestic political opposition by strangling the civilian population economically, and they make it more valuable to have close ties to the regime. More to the point, most people in a sanctioned country predictably blame the foreign governments that impose the sanctions for their hardships instead of faulting their own leaders, and that in turn gives the leaders a ready-made scapegoat towards which they can direct popular discontent. Furthermore, because sanctions harm the entire country, this can have the perverse effect of creating greater solidarity between the population and the regime than would be the case in the absence of foreign pressure. Because there is no significant political force in Iran that is willing to agree to maximalist hawkish demands on the nuclear issue, even successful regime change would not “solve” the nuclear issue to their satisfaction, because in the end the maximalist hawkish objection is to Iran’s role as a regional power.

There are also some concessions that no one in the current Iranian government will be prepared to accept. By insisting that Iran give up all enrichment, maximalists are demanding that Iran concede virtually everything on its side, which requires yielding on a point that both the regime and Iranian opposition leaders consider non-negotiable. Colin Kahl explained this in a recent briefing on Iran negotiations:

If Khamenei cries uncle and dismantles the entire Iranian program, how will he explain the tremendous expense and justify the years of sanctions and isolation to his people? What would it all have been for? Khamenei likely fears such a humiliation more than he fears economic collapse or targeted military strikes against his nuclear facilities.

Sanctions can’t force regime change, but they also can’t compel another government to agree to something that it considers to be utter humiliation.