Foreign Minister Hossein Amir-Abdollahian also said on Twitter that negotiations in Vienna were "proceeding with seriousness" and that the removal of sanctions was a "fundamental priority".

The talks resumed on Monday after Iran paused them in June after the election of ultraconservative President Ebrahim Raisi.

European diplomats had warned on Tuesday that "we don't have the luxury to spend time on niceties" and that they would assess the "seriousness" of Iran's position in the next 48 hours.

In his tweet on Thursday, Iran's foreign minister said the expert talks were continuing and that he was in daily contact with his deputy and lead negotiator, Ali Bagheri.

"Good deal within reach if the West shows good will. We seek rational, sober and result-oriented dialogue," said Amir-Abdollahian.

The goal of the Joint Comprehensive Plan of Action, or JCPOA, is to make it practically impossible for Iran to build an atomic bomb, while allowing it to pursue a civilian nuclear programme.

The 2015 accord offered Iran a lifting of economic sanctions in return for strict curbs on its nuclear activities.

But the deal started to unravel in 2018 when then US president Donald Trump pulled out and began imposing sanctions on the Islamic republic.

In turn, Iran, which denies it wants to acquire a nuclear arsenal, has gradually abandoned its commitments since 2019.

The remaining parties to the 2015 agreement -- Britain, China, France, Germany and Russia -- are participating directly in the Vienna talks. At Iran's insistence, the United States is doing so only indirectly.