They may not; and maybe they are using the negotiations to buy time while they build. But if the Iranians are honestly looking for an agreement that is fair to both side, they better waist no more time. The West is showing every sign of bad faith, including allowing Israel into the ante-room. Having said that, and as an American, I resent that Israel is using international Jewry to derail my country's attempts to improve its position in the Middle East.
UN to hold off on separate Afghan bombing probe for now (Reuters)
from the article: World powers demand Iran suspend work on Arak reactor