Iran's stance directly clashes with U.S. President Donald Trump 's position that Iran must halt all enrichment amid negotiations marked by uncertainty, despite having reached their most significant step since they began in April with a U.S. offer being delivered to Tehran last week.

An outline by the Trump administration would allow Iran to continue enriching uranium at low levels while a broader arrangement is worked out that would block the country’s path to a nuclear weapon.

A senior Iranian official told CNN the new nuclear deal proposal presented to Tehran in recent days is “incoherent and disjointed,” as sources familiar with the progress of the talks said the momentum behind negotiations to secure a new deal appears to be collapsing.