Foreign Minister Hossein Amir-Abdollahian was speaking at a joint news conference with visiting Russian counterpart Sergei Lavrov as talks between the parties in Vienna remain stalled.

"The nuclear negotiations train has reached difficult stops as they near the end," Amir-Abdollahian said.

He stressed Iran was "serious about reaching a good, strong and lasting agreement" and called for similar realism from the US side.

"I hope we can reach the final point of the agreement in the near future with realism from the American side," he said.

Russia was a party to the original 2015 deal -- the Joint Comprehensive Plan of Action, or JCPOA -- that gave Iran relief from international sanctions in return for UN-monitored limits to its nuclear activities.

It has taken part in the on-off talks that opened in Vienna in April last year on bringing Washington back into the agreement after president Donald's Trump 2018 withdrawal.

"Today, with the other participants in the JCPOA... we are making every effort to repair the American error when the United States left the JCPOA," Lavrov told the news conference.

Both Iran and Russia have been grappling with the economic impact of Western actions. Moscow has faced mounting sanctions since its invasion of neighbouring Ukraine in February.

"We oppose illegal sanctions against countries including Russia," Amir-Abdollahian said.