"We can confirm that we have received Iran's response through the EU," State Department spokesman Vedant Patel said late Thursday in Washington. "We are studying it and will respond through the EU, but unfortunately it is not constructive."

Kanani said on Monday that Tehran had "never received a response... saying that its position was not constructive".

He characterised Iran's response as "constructive, clear and legal".

"Iran is trying to cancel sanctions to economically benefit the Iranian nation and this is one of its top priorities," Kanani said.

The European Union put forward on 8 August what it called a final text to restore the 2015 nuclear accord, which was abandoned by former US president Donald Trump in 2018.

Talks to revive the 2015 accord known as the Joint Comprehensive Plan of Action have been on-going in Vienna since April 2021.

The deal granted Iran much-needed sanctions relief in return for curbs on its nuclear programme to prevent it from acquitting a nuclear weapon, a goal that Tehran has denied pursuing.