Iran wants rewards for showing compromise in the nuclear talks but the West does not want to remove sanctions in the early stages of a deal as reward for such compromise. The concern in the West is that once sanctions are removed, they will be difficult to impose again, if Iran starts to go against its word.
But the problem is: if the West does not reward Iran for positive steps taken, then the Iranians would have little incentive to continue showing compromise.
How can you satisfy both sides?
It seems that the US is coming up with a solution: instead of lifting sanctions at the early stages of a deal, reward Iran by allowing the Iranian government to have access to its frozen cash abroad, held in different bank accounts. Such accounts have been frozen as part of the sanctions.
So basically: money for compromise, for now.
The question is: will it be enough to keep the Iranians at the table?
At this stage, I would say its quite possible. The Iranian government needs access to its accounts badly.
But for the talks to be successful in the long term, the West needs to clearly spell out the sequencing of compromise by both sides. In other words, to clearly layout the map of what Iran will receive as reward, for which actions.
The sooner this is spelled out the better. Otherwise confusion, ambiguity and 34 years of mistrust between Iran and the US could make a difficult deal impossible.