The goal is to find a way back to the accord known by its acronym JCPOA, which former US president Donald Trump walked away from and which his successor Joe Biden wants to revive.
The stockpile of "enriched uranium will increase", he said, stressing that Tehran has the right within the deal to stop observing commitments "totally or partially" if the other parties fail to honour theirs.
"This gets us back into a position where we can work within that framework and work with our closest allies, in particular on addressing our concerns with Iran."