Former Ambassador Ryan Crocker describes previous experiences when negotiating with Iran has been successful, and gives an example of successful diplomacy that was sabotaged:

I continued to hold talks with the Iranians in Kabul when I was sent to reopen the United States Embassy there. We forged agreements on various security issues and coordinated approaches to reconstruction. And then, suddenly, it all came to an end when President George W. Bush gave his famous “Axis of Evil” speech in early 2002. The Iranian leadership concluded that in spite of their cooperation with the American war effort, the United States remained implacably hostile to the Islamic Republic [bold mine-DL].

Real cooperation effectively ceased after the speech and the costs were immediate. At the time, we were in the process of negotiating the transfer of the notorious Afghan warlord, Gulbuddin Hekmatyar, from Iranian house arrest to Afghan custody and ultimately to American control. Instead, the Iranians facilitated his covert entry into Afghanistan where he remains at large, launching attacks on coalition and Afghan targets.

It’s important to stress here that effectively sabotaging cooperation with Iran in 2002 with that stupid, gratuitous phrase didn’t advance anything that the U.S. was trying to do in the region. It ratcheted up tensions with Tehran and imposed costs on the U.S. for no purpose except to gratify some hard-liners in the administration. For most Americans, it probably sounded like a throwaway line, and for some it may have sounded like the sort of “tough” rhetoric that they think “strong” presidents use, but instead of conveying strength it reflected the clumsy incompetence that would define the administration in the years to come.

Crocker makes several suggestions for the current negotiations on the nuclear issue. Here were two that I found most interesting:

Third, America should be ready to introduce other issues beyond the nuclear file. Progress in one area can build confidence and facilitate progress in others. I mentioned this in a discussion with Iranian leaders in New York last month and they seemed receptive, mentioning Afghanistan and Syria as possibilities.

Finally, the United States must make clear that we do not seek to overthrow the Iranian regime. Iranian paranoia on this issue is virtually limitless and understandably so.

Including other issues in talks could be productive, but it would potentially create that many more obstacles to reaching any agreement. Once a few other issues are included in talks, either side could bring up new ones as a stalling tactic or an excuse to halt negotiations. Just as progress in one area can build confidence in others, setbacks can do the same to weaken it. Much of this would depend on the details. For instance, what exactly would the U.S. be negotiating with Iran about concerning Syria? Hard-liners in either country will seize on additional excuses to undermine the negotiations, so they should be given as few as possible. Clearly ruling out regime change is a good idea. That should make it easier for Iran to accept a deal that it might otherwise spurn, and it would also provoke many critics of diplomacy with Iran to show that their priority is overthrowing the government rather than resolving the nuclear issue. It should be a relatively easy guarantee for the U.S. to give Iran, and giving it would put Iranian hard-liners at a disadvantage by depriving them of a threat to demagogue.