Driving the cautious optimism, they say, is not so much progress made in overcoming sticking points as the intense political pressure on the U.S. and Iranian delegations to reach a deal that would end the 12-year nuclear stand-off between Iran and the West.

    “We can’t rule out failure, but … it seems more likely that we will get something. Not by June 30, but perhaps in the days that follow,” a senior Western official told Reuters, referring to the planned deadline for a deal.

Another Western official said: “I think there will be an agreement because the two most important players need it.”…

“There will be a deal, Americans need it more than we do. This deal will help both countries,” said an Iranian official, who put the chances of a final deal at 70 percent.