The nuclear deal between Iran and six world powers will face its first test this weekend. Inspectors from the International Atomic Energy Agency are due to make a long-delayed visit to a nuclear site in Iran where plutonium could be produced.
A nuclear reactor and associated production plant in Arak are a special concern because plutonium can be used in a nuclear bomb. Under last month's accord, Iran promised to allow inspections of its nuclear facilities.
Officials on both sides say they are committed to the nuclear deal, but keeping it on track will be a challenge.
Iranian officials also plan to meet next week with representatives from the United States and other countries to plan the next steps in implementing their deal.
Olli Heinonen, a longtime nuclear inspector, says this is the good news.
"There is now a process in place where the people are talking with each other," he says. "Whether they agree or disagree with each other, that's a different thing. But we got to the process."
The bad news? A deal might not be possible.
The overall concern is that Iran might develop a nuclear bomb.
Two Types Of Fuel
To keep that from happening, international watchdogs have to focus on two elements of a nuclear weapons program. The first is the fuel for a bomb — highly enriched uranium, or plutonium. The second is the design and manufacture of the explosive device itself — the nuclear warhead.
The accord reached in Geneva theoretically limits Iran's production of enriched uranium or plutonium — the fuel part. There's nothing about warhead research, at least not directly.
Parallels
Will Progress On Nuke Talks Mean More Engagement From Iran?