US President Donald Trump says he is extending sanctions relief for Iran one last time so Europe and the US can fix the nuclear deal's "terrible flaws".
The waiver he will sign suspends US sanctions on Iran for another 120 days.
The White House wants EU signatories to agree permanent restrictions on Iran's uranium enrichment. Under the current deal they are set to expire in 2025.
Iran's Foreign Minister Mohammad Javad Zarif said it was a "desperate attempt" to undermine a "solid" deal.
Mr Trump also wants Iran's ballistic missile programme to be addressed.
Also on Friday, the US imposed separate sanctions against 14 Iranian individuals and entities it accuses of rights abuses, censorship and support for weapons proliferators.
The US still maintains sanctions on Iran - independent of the nuclear deal - on matters such as terrorism, human rights and ballistic missile development.
The landmark accord was signed between six global powers and Iran in 2015.
It saw Iran agree to reduce uranium enrichment activity drastically, dispose of its enriched uranium stocks and modify a heavy water facility so it could not produce material suitable for a nuclear bomb, reports BBC.