It's their ultimate goal:
Obama: “If I had an option, if we could create an option in which Iran eliminated every single nut and bolt of their nuclear program, and foreswore the possibility of ever having a nuclear program, and, for that matter, got rid of all its military capabilities, I would take it,” he said, then added, “But that particular option is not available.”
One the other hand when Iran shows willingness and flexibility to give fully transparency IAEA takes no step:
Why Hasn’t the IAEA Followed Up Iran’s Inspection Offer?
Western countries think that sanctions and low oil prices could eventually bring Iran to its knees and make it to give up its NP, the same notion goes for negotiating table their assessment is pressure has forced Iran to comeback to the table ...
Therefore when we suspend our nuclear program and meanwhile sanctions still are out there and hurting , western power would keep current situation for good .